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diff DEPENDENCIES/mingw32/Python27/Lib/site-packages/numpy/lib/polynomial.py @ 87:2a2c65a20a8b
Add Python libs and headers
| author | Chris Cannam |
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| date | Wed, 25 Feb 2015 14:05:22 +0000 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/DEPENDENCIES/mingw32/Python27/Lib/site-packages/numpy/lib/polynomial.py Wed Feb 25 14:05:22 2015 +0000 @@ -0,0 +1,1271 @@ +""" +Functions to operate on polynomials. + +""" +from __future__ import division, absolute_import, print_function + +__all__ = ['poly', 'roots', 'polyint', 'polyder', 'polyadd', + 'polysub', 'polymul', 'polydiv', 'polyval', 'poly1d', + 'polyfit', 'RankWarning'] + +import re +import warnings +import numpy.core.numeric as NX + +from numpy.core import isscalar, abs, finfo, atleast_1d, hstack, dot +from numpy.lib.twodim_base import diag, vander +from numpy.lib.function_base import trim_zeros, sort_complex +from numpy.lib.type_check import iscomplex, real, imag +from numpy.linalg import eigvals, lstsq, inv + +class RankWarning(UserWarning): + """ + Issued by `polyfit` when the Vandermonde matrix is rank deficient. + + For more information, a way to suppress the warning, and an example of + `RankWarning` being issued, see `polyfit`. + + """ + pass + +def poly(seq_of_zeros): + """ + Find the coefficients of a polynomial with the given sequence of roots. + + Returns the coefficients of the polynomial whose leading coefficient + is one for the given sequence of zeros (multiple roots must be included + in the sequence as many times as their multiplicity; see Examples). + A square matrix (or array, which will be treated as a matrix) can also + be given, in which case the coefficients of the characteristic polynomial + of the matrix are returned. + + Parameters + ---------- + seq_of_zeros : array_like, shape (N,) or (N, N) + A sequence of polynomial roots, or a square array or matrix object. + + Returns + ------- + c : ndarray + 1D array of polynomial coefficients from highest to lowest degree: + + ``c[0] * x**(N) + c[1] * x**(N-1) + ... + c[N-1] * x + c[N]`` + where c[0] always equals 1. + + Raises + ------ + ValueError + If input is the wrong shape (the input must be a 1-D or square + 2-D array). + + See Also + -------- + polyval : Evaluate a polynomial at a point. + roots : Return the roots of a polynomial. + polyfit : Least squares polynomial fit. + poly1d : A one-dimensional polynomial class. + + Notes + ----- + Specifying the roots of a polynomial still leaves one degree of + freedom, typically represented by an undetermined leading + coefficient. [1]_ In the case of this function, that coefficient - + the first one in the returned array - is always taken as one. (If + for some reason you have one other point, the only automatic way + presently to leverage that information is to use ``polyfit``.) + + The characteristic polynomial, :math:`p_a(t)`, of an `n`-by-`n` + matrix **A** is given by + + :math:`p_a(t) = \\mathrm{det}(t\\, \\mathbf{I} - \\mathbf{A})`, + + where **I** is the `n`-by-`n` identity matrix. [2]_ + + References + ---------- + .. [1] M. Sullivan and M. Sullivan, III, "Algebra and Trignometry, + Enhanced With Graphing Utilities," Prentice-Hall, pg. 318, 1996. + + .. [2] G. Strang, "Linear Algebra and Its Applications, 2nd Edition," + Academic Press, pg. 182, 1980. + + Examples + -------- + Given a sequence of a polynomial's zeros: + + >>> np.poly((0, 0, 0)) # Multiple root example + array([1, 0, 0, 0]) + + The line above represents z**3 + 0*z**2 + 0*z + 0. + + >>> np.poly((-1./2, 0, 1./2)) + array([ 1. , 0. , -0.25, 0. ]) + + The line above represents z**3 - z/4 + + >>> np.poly((np.random.random(1.)[0], 0, np.random.random(1.)[0])) + array([ 1. , -0.77086955, 0.08618131, 0. ]) #random + + Given a square array object: + + >>> P = np.array([[0, 1./3], [-1./2, 0]]) + >>> np.poly(P) + array([ 1. , 0. , 0.16666667]) + + Or a square matrix object: + + >>> np.poly(np.matrix(P)) + array([ 1. , 0. , 0.16666667]) + + Note how in all cases the leading coefficient is always 1. + + """ + seq_of_zeros = atleast_1d(seq_of_zeros) + sh = seq_of_zeros.shape + if len(sh) == 2 and sh[0] == sh[1] and sh[0] != 0: + seq_of_zeros = eigvals(seq_of_zeros) + elif len(sh) == 1: + pass + else: + raise ValueError("input must be 1d or non-empty square 2d array.") + + if len(seq_of_zeros) == 0: + return 1.0 + + a = [1] + for k in range(len(seq_of_zeros)): + a = NX.convolve(a, [1, -seq_of_zeros[k]], mode='full') + + if issubclass(a.dtype.type, NX.complexfloating): + # if complex roots are all complex conjugates, the roots are real. + roots = NX.asarray(seq_of_zeros, complex) + pos_roots = sort_complex(NX.compress(roots.imag > 0, roots)) + neg_roots = NX.conjugate(sort_complex( + NX.compress(roots.imag < 0, roots))) + if (len(pos_roots) == len(neg_roots) and + NX.alltrue(neg_roots == pos_roots)): + a = a.real.copy() + + return a + +def roots(p): + """ + Return the roots of a polynomial with coefficients given in p. + + The values in the rank-1 array `p` are coefficients of a polynomial. + If the length of `p` is n+1 then the polynomial is described by:: + + p[0] * x**n + p[1] * x**(n-1) + ... + p[n-1]*x + p[n] + + Parameters + ---------- + p : array_like + Rank-1 array of polynomial coefficients. + + Returns + ------- + out : ndarray + An array containing the complex roots of the polynomial. + + Raises + ------ + ValueError + When `p` cannot be converted to a rank-1 array. + + See also + -------- + poly : Find the coefficients of a polynomial with a given sequence + of roots. + polyval : Evaluate a polynomial at a point. + polyfit : Least squares polynomial fit. + poly1d : A one-dimensional polynomial class. + + Notes + ----- + The algorithm relies on computing the eigenvalues of the + companion matrix [1]_. + + References + ---------- + .. [1] R. A. Horn & C. R. Johnson, *Matrix Analysis*. Cambridge, UK: + Cambridge University Press, 1999, pp. 146-7. + + Examples + -------- + >>> coeff = [3.2, 2, 1] + >>> np.roots(coeff) + array([-0.3125+0.46351241j, -0.3125-0.46351241j]) + + """ + # If input is scalar, this makes it an array + p = atleast_1d(p) + if len(p.shape) != 1: + raise ValueError("Input must be a rank-1 array.") + + # find non-zero array entries + non_zero = NX.nonzero(NX.ravel(p))[0] + + # Return an empty array if polynomial is all zeros + if len(non_zero) == 0: + return NX.array([]) + + # find the number of trailing zeros -- this is the number of roots at 0. + trailing_zeros = len(p) - non_zero[-1] - 1 + + # strip leading and trailing zeros + p = p[int(non_zero[0]):int(non_zero[-1])+1] + + # casting: if incoming array isn't floating point, make it floating point. + if not issubclass(p.dtype.type, (NX.floating, NX.complexfloating)): + p = p.astype(float) + + N = len(p) + if N > 1: + # build companion matrix and find its eigenvalues (the roots) + A = diag(NX.ones((N-2,), p.dtype), -1) + A[0,:] = -p[1:] / p[0] + roots = eigvals(A) + else: + roots = NX.array([]) + + # tack any zeros onto the back of the array + roots = hstack((roots, NX.zeros(trailing_zeros, roots.dtype))) + return roots + +def polyint(p, m=1, k=None): + """ + Return an antiderivative (indefinite integral) of a polynomial. + + The returned order `m` antiderivative `P` of polynomial `p` satisfies + :math:`\\frac{d^m}{dx^m}P(x) = p(x)` and is defined up to `m - 1` + integration constants `k`. The constants determine the low-order + polynomial part + + .. math:: \\frac{k_{m-1}}{0!} x^0 + \\ldots + \\frac{k_0}{(m-1)!}x^{m-1} + + of `P` so that :math:`P^{(j)}(0) = k_{m-j-1}`. + + Parameters + ---------- + p : {array_like, poly1d} + Polynomial to differentiate. + A sequence is interpreted as polynomial coefficients, see `poly1d`. + m : int, optional + Order of the antiderivative. (Default: 1) + k : {None, list of `m` scalars, scalar}, optional + Integration constants. They are given in the order of integration: + those corresponding to highest-order terms come first. + + If ``None`` (default), all constants are assumed to be zero. + If `m = 1`, a single scalar can be given instead of a list. + + See Also + -------- + polyder : derivative of a polynomial + poly1d.integ : equivalent method + + Examples + -------- + The defining property of the antiderivative: + + >>> p = np.poly1d([1,1,1]) + >>> P = np.polyint(p) + >>> P + poly1d([ 0.33333333, 0.5 , 1. , 0. ]) + >>> np.polyder(P) == p + True + + The integration constants default to zero, but can be specified: + + >>> P = np.polyint(p, 3) + >>> P(0) + 0.0 + >>> np.polyder(P)(0) + 0.0 + >>> np.polyder(P, 2)(0) + 0.0 + >>> P = np.polyint(p, 3, k=[6,5,3]) + >>> P + poly1d([ 0.01666667, 0.04166667, 0.16666667, 3. , 5. , 3. ]) + + Note that 3 = 6 / 2!, and that the constants are given in the order of + integrations. Constant of the highest-order polynomial term comes first: + + >>> np.polyder(P, 2)(0) + 6.0 + >>> np.polyder(P, 1)(0) + 5.0 + >>> P(0) + 3.0 + + """ + m = int(m) + if m < 0: + raise ValueError("Order of integral must be positive (see polyder)") + if k is None: + k = NX.zeros(m, float) + k = atleast_1d(k) + if len(k) == 1 and m > 1: + k = k[0]*NX.ones(m, float) + if len(k) < m: + raise ValueError( + "k must be a scalar or a rank-1 array of length 1 or >m.") + + truepoly = isinstance(p, poly1d) + p = NX.asarray(p) + if m == 0: + if truepoly: + return poly1d(p) + return p + else: + # Note: this must work also with object and integer arrays + y = NX.concatenate((p.__truediv__(NX.arange(len(p), 0, -1)), [k[0]])) + val = polyint(y, m - 1, k=k[1:]) + if truepoly: + return poly1d(val) + return val + +def polyder(p, m=1): + """ + Return the derivative of the specified order of a polynomial. + + Parameters + ---------- + p : poly1d or sequence + Polynomial to differentiate. + A sequence is interpreted as polynomial coefficients, see `poly1d`. + m : int, optional + Order of differentiation (default: 1) + + Returns + ------- + der : poly1d + A new polynomial representing the derivative. + + See Also + -------- + polyint : Anti-derivative of a polynomial. + poly1d : Class for one-dimensional polynomials. + + Examples + -------- + The derivative of the polynomial :math:`x^3 + x^2 + x^1 + 1` is: + + >>> p = np.poly1d([1,1,1,1]) + >>> p2 = np.polyder(p) + >>> p2 + poly1d([3, 2, 1]) + + which evaluates to: + + >>> p2(2.) + 17.0 + + We can verify this, approximating the derivative with + ``(f(x + h) - f(x))/h``: + + >>> (p(2. + 0.001) - p(2.)) / 0.001 + 17.007000999997857 + + The fourth-order derivative of a 3rd-order polynomial is zero: + + >>> np.polyder(p, 2) + poly1d([6, 2]) + >>> np.polyder(p, 3) + poly1d([6]) + >>> np.polyder(p, 4) + poly1d([ 0.]) + + """ + m = int(m) + if m < 0: + raise ValueError("Order of derivative must be positive (see polyint)") + + truepoly = isinstance(p, poly1d) + p = NX.asarray(p) + n = len(p) - 1 + y = p[:-1] * NX.arange(n, 0, -1) + if m == 0: + val = p + else: + val = polyder(y, m - 1) + if truepoly: + val = poly1d(val) + return val + +def polyfit(x, y, deg, rcond=None, full=False, w=None, cov=False): + """ + Least squares polynomial fit. + + Fit a polynomial ``p(x) = p[0] * x**deg + ... + p[deg]`` of degree `deg` + to points `(x, y)`. Returns a vector of coefficients `p` that minimises + the squared error. + + Parameters + ---------- + x : array_like, shape (M,) + x-coordinates of the M sample points ``(x[i], y[i])``. + y : array_like, shape (M,) or (M, K) + y-coordinates of the sample points. Several data sets of sample + points sharing the same x-coordinates can be fitted at once by + passing in a 2D-array that contains one dataset per column. + deg : int + Degree of the fitting polynomial + rcond : float, optional + Relative condition number of the fit. Singular values smaller than + this relative to the largest singular value will be ignored. The + default value is len(x)*eps, where eps is the relative precision of + the float type, about 2e-16 in most cases. + full : bool, optional + Switch determining nature of return value. When it is False (the + default) just the coefficients are returned, when True diagnostic + information from the singular value decomposition is also returned. + w : array_like, shape (M,), optional + weights to apply to the y-coordinates of the sample points. + cov : bool, optional + Return the estimate and the covariance matrix of the estimate + If full is True, then cov is not returned. + + Returns + ------- + p : ndarray, shape (M,) or (M, K) + Polynomial coefficients, highest power first. If `y` was 2-D, the + coefficients for `k`-th data set are in ``p[:,k]``. + + residuals, rank, singular_values, rcond : + Present only if `full` = True. Residuals of the least-squares fit, + the effective rank of the scaled Vandermonde coefficient matrix, + its singular values, and the specified value of `rcond`. For more + details, see `linalg.lstsq`. + + V : ndarray, shape (M,M) or (M,M,K) + Present only if `full` = False and `cov`=True. The covariance + matrix of the polynomial coefficient estimates. The diagonal of + this matrix are the variance estimates for each coefficient. If y + is a 2-D array, then the covariance matrix for the `k`-th data set + are in ``V[:,:,k]`` + + + Warns + ----- + RankWarning + The rank of the coefficient matrix in the least-squares fit is + deficient. The warning is only raised if `full` = False. + + The warnings can be turned off by + + >>> import warnings + >>> warnings.simplefilter('ignore', np.RankWarning) + + See Also + -------- + polyval : Computes polynomial values. + linalg.lstsq : Computes a least-squares fit. + scipy.interpolate.UnivariateSpline : Computes spline fits. + + Notes + ----- + The solution minimizes the squared error + + .. math :: + E = \\sum_{j=0}^k |p(x_j) - y_j|^2 + + in the equations:: + + x[0]**n * p[0] + ... + x[0] * p[n-1] + p[n] = y[0] + x[1]**n * p[0] + ... + x[1] * p[n-1] + p[n] = y[1] + ... + x[k]**n * p[0] + ... + x[k] * p[n-1] + p[n] = y[k] + + The coefficient matrix of the coefficients `p` is a Vandermonde matrix. + + `polyfit` issues a `RankWarning` when the least-squares fit is badly + conditioned. This implies that the best fit is not well-defined due + to numerical error. The results may be improved by lowering the polynomial + degree or by replacing `x` by `x` - `x`.mean(). The `rcond` parameter + can also be set to a value smaller than its default, but the resulting + fit may be spurious: including contributions from the small singular + values can add numerical noise to the result. + + Note that fitting polynomial coefficients is inherently badly conditioned + when the degree of the polynomial is large or the interval of sample points + is badly centered. The quality of the fit should always be checked in these + cases. When polynomial fits are not satisfactory, splines may be a good + alternative. + + References + ---------- + .. [1] Wikipedia, "Curve fitting", + http://en.wikipedia.org/wiki/Curve_fitting + .. [2] Wikipedia, "Polynomial interpolation", + http://en.wikipedia.org/wiki/Polynomial_interpolation + + Examples + -------- + >>> x = np.array([0.0, 1.0, 2.0, 3.0, 4.0, 5.0]) + >>> y = np.array([0.0, 0.8, 0.9, 0.1, -0.8, -1.0]) + >>> z = np.polyfit(x, y, 3) + >>> z + array([ 0.08703704, -0.81349206, 1.69312169, -0.03968254]) + + It is convenient to use `poly1d` objects for dealing with polynomials: + + >>> p = np.poly1d(z) + >>> p(0.5) + 0.6143849206349179 + >>> p(3.5) + -0.34732142857143039 + >>> p(10) + 22.579365079365115 + + High-order polynomials may oscillate wildly: + + >>> p30 = np.poly1d(np.polyfit(x, y, 30)) + /... RankWarning: Polyfit may be poorly conditioned... + >>> p30(4) + -0.80000000000000204 + >>> p30(5) + -0.99999999999999445 + >>> p30(4.5) + -0.10547061179440398 + + Illustration: + + >>> import matplotlib.pyplot as plt + >>> xp = np.linspace(-2, 6, 100) + >>> _ = plt.plot(x, y, '.', xp, p(xp), '-', xp, p30(xp), '--') + >>> plt.ylim(-2,2) + (-2, 2) + >>> plt.show() + + """ + order = int(deg) + 1 + x = NX.asarray(x) + 0.0 + y = NX.asarray(y) + 0.0 + + # check arguments. + if deg < 0: + raise ValueError("expected deg >= 0") + if x.ndim != 1: + raise TypeError("expected 1D vector for x") + if x.size == 0: + raise TypeError("expected non-empty vector for x") + if y.ndim < 1 or y.ndim > 2: + raise TypeError("expected 1D or 2D array for y") + if x.shape[0] != y.shape[0]: + raise TypeError("expected x and y to have same length") + + # set rcond + if rcond is None: + rcond = len(x)*finfo(x.dtype).eps + + # set up least squares equation for powers of x + lhs = vander(x, order) + rhs = y + + # apply weighting + if w is not None: + w = NX.asarray(w) + 0.0 + if w.ndim != 1: + raise TypeError("expected a 1-d array for weights") + if w.shape[0] != y.shape[0]: + raise TypeError("expected w and y to have the same length") + lhs *= w[:, NX.newaxis] + if rhs.ndim == 2: + rhs *= w[:, NX.newaxis] + else: + rhs *= w + + # scale lhs to improve condition number and solve + scale = NX.sqrt((lhs*lhs).sum(axis=0)) + lhs /= scale + c, resids, rank, s = lstsq(lhs, rhs, rcond) + c = (c.T/scale).T # broadcast scale coefficients + + # warn on rank reduction, which indicates an ill conditioned matrix + if rank != order and not full: + msg = "Polyfit may be poorly conditioned" + warnings.warn(msg, RankWarning) + + if full: + return c, resids, rank, s, rcond + elif cov: + Vbase = inv(dot(lhs.T, lhs)) + Vbase /= NX.outer(scale, scale) + # Some literature ignores the extra -2.0 factor in the denominator, but + # it is included here because the covariance of Multivariate Student-T + # (which is implied by a Bayesian uncertainty analysis) includes it. + # Plus, it gives a slightly more conservative estimate of uncertainty. + fac = resids / (len(x) - order - 2.0) + if y.ndim == 1: + return c, Vbase * fac + else: + return c, Vbase[:,:, NX.newaxis] * fac + else: + return c + + +def polyval(p, x): + """ + Evaluate a polynomial at specific values. + + If `p` is of length N, this function returns the value: + + ``p[0]*x**(N-1) + p[1]*x**(N-2) + ... + p[N-2]*x + p[N-1]`` + + If `x` is a sequence, then `p(x)` is returned for each element of `x`. + If `x` is another polynomial then the composite polynomial `p(x(t))` + is returned. + + Parameters + ---------- + p : array_like or poly1d object + 1D array of polynomial coefficients (including coefficients equal + to zero) from highest degree to the constant term, or an + instance of poly1d. + x : array_like or poly1d object + A number, a 1D array of numbers, or an instance of poly1d, "at" + which to evaluate `p`. + + Returns + ------- + values : ndarray or poly1d + If `x` is a poly1d instance, the result is the composition of the two + polynomials, i.e., `x` is "substituted" in `p` and the simplified + result is returned. In addition, the type of `x` - array_like or + poly1d - governs the type of the output: `x` array_like => `values` + array_like, `x` a poly1d object => `values` is also. + + See Also + -------- + poly1d: A polynomial class. + + Notes + ----- + Horner's scheme [1]_ is used to evaluate the polynomial. Even so, + for polynomials of high degree the values may be inaccurate due to + rounding errors. Use carefully. + + References + ---------- + .. [1] I. N. Bronshtein, K. A. Semendyayev, and K. A. Hirsch (Eng. + trans. Ed.), *Handbook of Mathematics*, New York, Van Nostrand + Reinhold Co., 1985, pg. 720. + + Examples + -------- + >>> np.polyval([3,0,1], 5) # 3 * 5**2 + 0 * 5**1 + 1 + 76 + >>> np.polyval([3,0,1], np.poly1d(5)) + poly1d([ 76.]) + >>> np.polyval(np.poly1d([3,0,1]), 5) + 76 + >>> np.polyval(np.poly1d([3,0,1]), np.poly1d(5)) + poly1d([ 76.]) + + """ + p = NX.asarray(p) + if isinstance(x, poly1d): + y = 0 + else: + x = NX.asarray(x) + y = NX.zeros_like(x) + for i in range(len(p)): + y = x * y + p[i] + return y + +def polyadd(a1, a2): + """ + Find the sum of two polynomials. + + Returns the polynomial resulting from the sum of two input polynomials. + Each input must be either a poly1d object or a 1D sequence of polynomial + coefficients, from highest to lowest degree. + + Parameters + ---------- + a1, a2 : array_like or poly1d object + Input polynomials. + + Returns + ------- + out : ndarray or poly1d object + The sum of the inputs. If either input is a poly1d object, then the + output is also a poly1d object. Otherwise, it is a 1D array of + polynomial coefficients from highest to lowest degree. + + See Also + -------- + poly1d : A one-dimensional polynomial class. + poly, polyadd, polyder, polydiv, polyfit, polyint, polysub, polyval + + Examples + -------- + >>> np.polyadd([1, 2], [9, 5, 4]) + array([9, 6, 6]) + + Using poly1d objects: + + >>> p1 = np.poly1d([1, 2]) + >>> p2 = np.poly1d([9, 5, 4]) + >>> print p1 + 1 x + 2 + >>> print p2 + 2 + 9 x + 5 x + 4 + >>> print np.polyadd(p1, p2) + 2 + 9 x + 6 x + 6 + + """ + truepoly = (isinstance(a1, poly1d) or isinstance(a2, poly1d)) + a1 = atleast_1d(a1) + a2 = atleast_1d(a2) + diff = len(a2) - len(a1) + if diff == 0: + val = a1 + a2 + elif diff > 0: + zr = NX.zeros(diff, a1.dtype) + val = NX.concatenate((zr, a1)) + a2 + else: + zr = NX.zeros(abs(diff), a2.dtype) + val = a1 + NX.concatenate((zr, a2)) + if truepoly: + val = poly1d(val) + return val + +def polysub(a1, a2): + """ + Difference (subtraction) of two polynomials. + + Given two polynomials `a1` and `a2`, returns ``a1 - a2``. + `a1` and `a2` can be either array_like sequences of the polynomials' + coefficients (including coefficients equal to zero), or `poly1d` objects. + + Parameters + ---------- + a1, a2 : array_like or poly1d + Minuend and subtrahend polynomials, respectively. + + Returns + ------- + out : ndarray or poly1d + Array or `poly1d` object of the difference polynomial's coefficients. + + See Also + -------- + polyval, polydiv, polymul, polyadd + + Examples + -------- + .. math:: (2 x^2 + 10 x - 2) - (3 x^2 + 10 x -4) = (-x^2 + 2) + + >>> np.polysub([2, 10, -2], [3, 10, -4]) + array([-1, 0, 2]) + + """ + truepoly = (isinstance(a1, poly1d) or isinstance(a2, poly1d)) + a1 = atleast_1d(a1) + a2 = atleast_1d(a2) + diff = len(a2) - len(a1) + if diff == 0: + val = a1 - a2 + elif diff > 0: + zr = NX.zeros(diff, a1.dtype) + val = NX.concatenate((zr, a1)) - a2 + else: + zr = NX.zeros(abs(diff), a2.dtype) + val = a1 - NX.concatenate((zr, a2)) + if truepoly: + val = poly1d(val) + return val + + +def polymul(a1, a2): + """ + Find the product of two polynomials. + + Finds the polynomial resulting from the multiplication of the two input + polynomials. Each input must be either a poly1d object or a 1D sequence + of polynomial coefficients, from highest to lowest degree. + + Parameters + ---------- + a1, a2 : array_like or poly1d object + Input polynomials. + + Returns + ------- + out : ndarray or poly1d object + The polynomial resulting from the multiplication of the inputs. If + either inputs is a poly1d object, then the output is also a poly1d + object. Otherwise, it is a 1D array of polynomial coefficients from + highest to lowest degree. + + See Also + -------- + poly1d : A one-dimensional polynomial class. + poly, polyadd, polyder, polydiv, polyfit, polyint, polysub, + polyval + convolve : Array convolution. Same output as polymul, but has parameter + for overlap mode. + + Examples + -------- + >>> np.polymul([1, 2, 3], [9, 5, 1]) + array([ 9, 23, 38, 17, 3]) + + Using poly1d objects: + + >>> p1 = np.poly1d([1, 2, 3]) + >>> p2 = np.poly1d([9, 5, 1]) + >>> print p1 + 2 + 1 x + 2 x + 3 + >>> print p2 + 2 + 9 x + 5 x + 1 + >>> print np.polymul(p1, p2) + 4 3 2 + 9 x + 23 x + 38 x + 17 x + 3 + + """ + truepoly = (isinstance(a1, poly1d) or isinstance(a2, poly1d)) + a1, a2 = poly1d(a1), poly1d(a2) + val = NX.convolve(a1, a2) + if truepoly: + val = poly1d(val) + return val + +def polydiv(u, v): + """ + Returns the quotient and remainder of polynomial division. + + The input arrays are the coefficients (including any coefficients + equal to zero) of the "numerator" (dividend) and "denominator" + (divisor) polynomials, respectively. + + Parameters + ---------- + u : array_like or poly1d + Dividend polynomial's coefficients. + + v : array_like or poly1d + Divisor polynomial's coefficients. + + Returns + ------- + q : ndarray + Coefficients, including those equal to zero, of the quotient. + r : ndarray + Coefficients, including those equal to zero, of the remainder. + + See Also + -------- + poly, polyadd, polyder, polydiv, polyfit, polyint, polymul, polysub, + polyval + + Notes + ----- + Both `u` and `v` must be 0-d or 1-d (ndim = 0 or 1), but `u.ndim` need + not equal `v.ndim`. In other words, all four possible combinations - + ``u.ndim = v.ndim = 0``, ``u.ndim = v.ndim = 1``, + ``u.ndim = 1, v.ndim = 0``, and ``u.ndim = 0, v.ndim = 1`` - work. + + Examples + -------- + .. math:: \\frac{3x^2 + 5x + 2}{2x + 1} = 1.5x + 1.75, remainder 0.25 + + >>> x = np.array([3.0, 5.0, 2.0]) + >>> y = np.array([2.0, 1.0]) + >>> np.polydiv(x, y) + (array([ 1.5 , 1.75]), array([ 0.25])) + + """ + truepoly = (isinstance(u, poly1d) or isinstance(u, poly1d)) + u = atleast_1d(u) + 0.0 + v = atleast_1d(v) + 0.0 + # w has the common type + w = u[0] + v[0] + m = len(u) - 1 + n = len(v) - 1 + scale = 1. / v[0] + q = NX.zeros((max(m - n + 1, 1),), w.dtype) + r = u.copy() + for k in range(0, m-n+1): + d = scale * r[k] + q[k] = d + r[k:k+n+1] -= d*v + while NX.allclose(r[0], 0, rtol=1e-14) and (r.shape[-1] > 1): + r = r[1:] + if truepoly: + return poly1d(q), poly1d(r) + return q, r + +_poly_mat = re.compile(r"[*][*]([0-9]*)") +def _raise_power(astr, wrap=70): + n = 0 + line1 = '' + line2 = '' + output = ' ' + while True: + mat = _poly_mat.search(astr, n) + if mat is None: + break + span = mat.span() + power = mat.groups()[0] + partstr = astr[n:span[0]] + n = span[1] + toadd2 = partstr + ' '*(len(power)-1) + toadd1 = ' '*(len(partstr)-1) + power + if ((len(line2) + len(toadd2) > wrap) or + (len(line1) + len(toadd1) > wrap)): + output += line1 + "\n" + line2 + "\n " + line1 = toadd1 + line2 = toadd2 + else: + line2 += partstr + ' '*(len(power)-1) + line1 += ' '*(len(partstr)-1) + power + output += line1 + "\n" + line2 + return output + astr[n:] + + +class poly1d(object): + """ + A one-dimensional polynomial class. + + A convenience class, used to encapsulate "natural" operations on + polynomials so that said operations may take on their customary + form in code (see Examples). + + Parameters + ---------- + c_or_r : array_like + The polynomial's coefficients, in decreasing powers, or if + the value of the second parameter is True, the polynomial's + roots (values where the polynomial evaluates to 0). For example, + ``poly1d([1, 2, 3])`` returns an object that represents + :math:`x^2 + 2x + 3`, whereas ``poly1d([1, 2, 3], True)`` returns + one that represents :math:`(x-1)(x-2)(x-3) = x^3 - 6x^2 + 11x -6`. + r : bool, optional + If True, `c_or_r` specifies the polynomial's roots; the default + is False. + variable : str, optional + Changes the variable used when printing `p` from `x` to `variable` + (see Examples). + + Examples + -------- + Construct the polynomial :math:`x^2 + 2x + 3`: + + >>> p = np.poly1d([1, 2, 3]) + >>> print np.poly1d(p) + 2 + 1 x + 2 x + 3 + + Evaluate the polynomial at :math:`x = 0.5`: + + >>> p(0.5) + 4.25 + + Find the roots: + + >>> p.r + array([-1.+1.41421356j, -1.-1.41421356j]) + >>> p(p.r) + array([ -4.44089210e-16+0.j, -4.44089210e-16+0.j]) + + These numbers in the previous line represent (0, 0) to machine precision + + Show the coefficients: + + >>> p.c + array([1, 2, 3]) + + Display the order (the leading zero-coefficients are removed): + + >>> p.order + 2 + + Show the coefficient of the k-th power in the polynomial + (which is equivalent to ``p.c[-(i+1)]``): + + >>> p[1] + 2 + + Polynomials can be added, subtracted, multiplied, and divided + (returns quotient and remainder): + + >>> p * p + poly1d([ 1, 4, 10, 12, 9]) + + >>> (p**3 + 4) / p + (poly1d([ 1., 4., 10., 12., 9.]), poly1d([ 4.])) + + ``asarray(p)`` gives the coefficient array, so polynomials can be + used in all functions that accept arrays: + + >>> p**2 # square of polynomial + poly1d([ 1, 4, 10, 12, 9]) + + >>> np.square(p) # square of individual coefficients + array([1, 4, 9]) + + The variable used in the string representation of `p` can be modified, + using the `variable` parameter: + + >>> p = np.poly1d([1,2,3], variable='z') + >>> print p + 2 + 1 z + 2 z + 3 + + Construct a polynomial from its roots: + + >>> np.poly1d([1, 2], True) + poly1d([ 1, -3, 2]) + + This is the same polynomial as obtained by: + + >>> np.poly1d([1, -1]) * np.poly1d([1, -2]) + poly1d([ 1, -3, 2]) + + """ + coeffs = None + order = None + variable = None + __hash__ = None + + def __init__(self, c_or_r, r=0, variable=None): + if isinstance(c_or_r, poly1d): + for key in c_or_r.__dict__.keys(): + self.__dict__[key] = c_or_r.__dict__[key] + if variable is not None: + self.__dict__['variable'] = variable + return + if r: + c_or_r = poly(c_or_r) + c_or_r = atleast_1d(c_or_r) + if len(c_or_r.shape) > 1: + raise ValueError("Polynomial must be 1d only.") + c_or_r = trim_zeros(c_or_r, trim='f') + if len(c_or_r) == 0: + c_or_r = NX.array([0.]) + self.__dict__['coeffs'] = c_or_r + self.__dict__['order'] = len(c_or_r) - 1 + if variable is None: + variable = 'x' + self.__dict__['variable'] = variable + + def __array__(self, t=None): + if t: + return NX.asarray(self.coeffs, t) + else: + return NX.asarray(self.coeffs) + + def __repr__(self): + vals = repr(self.coeffs) + vals = vals[6:-1] + return "poly1d(%s)" % vals + + def __len__(self): + return self.order + + def __str__(self): + thestr = "0" + var = self.variable + + # Remove leading zeros + coeffs = self.coeffs[NX.logical_or.accumulate(self.coeffs != 0)] + N = len(coeffs)-1 + + def fmt_float(q): + s = '%.4g' % q + if s.endswith('.0000'): + s = s[:-5] + return s + + for k in range(len(coeffs)): + if not iscomplex(coeffs[k]): + coefstr = fmt_float(real(coeffs[k])) + elif real(coeffs[k]) == 0: + coefstr = '%sj' % fmt_float(imag(coeffs[k])) + else: + coefstr = '(%s + %sj)' % (fmt_float(real(coeffs[k])), + fmt_float(imag(coeffs[k]))) + + power = (N-k) + if power == 0: + if coefstr != '0': + newstr = '%s' % (coefstr,) + else: + if k == 0: + newstr = '0' + else: + newstr = '' + elif power == 1: + if coefstr == '0': + newstr = '' + elif coefstr == 'b': + newstr = var + else: + newstr = '%s %s' % (coefstr, var) + else: + if coefstr == '0': + newstr = '' + elif coefstr == 'b': + newstr = '%s**%d' % (var, power,) + else: + newstr = '%s %s**%d' % (coefstr, var, power) + + if k > 0: + if newstr != '': + if newstr.startswith('-'): + thestr = "%s - %s" % (thestr, newstr[1:]) + else: + thestr = "%s + %s" % (thestr, newstr) + else: + thestr = newstr + return _raise_power(thestr) + + def __call__(self, val): + return polyval(self.coeffs, val) + + def __neg__(self): + return poly1d(-self.coeffs) + + def __pos__(self): + return self + + def __mul__(self, other): + if isscalar(other): + return poly1d(self.coeffs * other) + else: + other = poly1d(other) + return poly1d(polymul(self.coeffs, other.coeffs)) + + def __rmul__(self, other): + if isscalar(other): + return poly1d(other * self.coeffs) + else: + other = poly1d(other) + return poly1d(polymul(self.coeffs, other.coeffs)) + + def __add__(self, other): + other = poly1d(other) + return poly1d(polyadd(self.coeffs, other.coeffs)) + + def __radd__(self, other): + other = poly1d(other) + return poly1d(polyadd(self.coeffs, other.coeffs)) + + def __pow__(self, val): + if not isscalar(val) or int(val) != val or val < 0: + raise ValueError("Power to non-negative integers only.") + res = [1] + for _ in range(val): + res = polymul(self.coeffs, res) + return poly1d(res) + + def __sub__(self, other): + other = poly1d(other) + return poly1d(polysub(self.coeffs, other.coeffs)) + + def __rsub__(self, other): + other = poly1d(other) + return poly1d(polysub(other.coeffs, self.coeffs)) + + def __div__(self, other): + if isscalar(other): + return poly1d(self.coeffs/other) + else: + other = poly1d(other) + return polydiv(self, other) + + __truediv__ = __div__ + + def __rdiv__(self, other): + if isscalar(other): + return poly1d(other/self.coeffs) + else: + other = poly1d(other) + return polydiv(other, self) + + __rtruediv__ = __rdiv__ + + def __eq__(self, other): + if self.coeffs.shape != other.coeffs.shape: + return False + return (self.coeffs == other.coeffs).all() + + def __ne__(self, other): + return not self.__eq__(other) + + def __setattr__(self, key, val): + raise ValueError("Attributes cannot be changed this way.") + + def __getattr__(self, key): + if key in ['r', 'roots']: + return roots(self.coeffs) + elif key in ['c', 'coef', 'coefficients']: + return self.coeffs + elif key in ['o']: + return self.order + else: + try: + return self.__dict__[key] + except KeyError: + raise AttributeError( + "'%s' has no attribute '%s'" % (self.__class__, key)) + + def __getitem__(self, val): + ind = self.order - val + if val > self.order: + return 0 + if val < 0: + return 0 + return self.coeffs[ind] + + def __setitem__(self, key, val): + ind = self.order - key + if key < 0: + raise ValueError("Does not support negative powers.") + if key > self.order: + zr = NX.zeros(key-self.order, self.coeffs.dtype) + self.__dict__['coeffs'] = NX.concatenate((zr, self.coeffs)) + self.__dict__['order'] = key + ind = 0 + self.__dict__['coeffs'][ind] = val + return + + def __iter__(self): + return iter(self.coeffs) + + def integ(self, m=1, k=0): + """ + Return an antiderivative (indefinite integral) of this polynomial. + + Refer to `polyint` for full documentation. + + See Also + -------- + polyint : equivalent function + + """ + return poly1d(polyint(self.coeffs, m=m, k=k)) + + def deriv(self, m=1): + """ + Return a derivative of this polynomial. + + Refer to `polyder` for full documentation. + + See Also + -------- + polyder : equivalent function + + """ + return poly1d(polyder(self.coeffs, m=m)) + +# Stuff to do on module import + +warnings.simplefilter('always', RankWarning)