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1 .TH SMOOTH 1 "1 September 1993"
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2
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3 .SH NAME
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4 smooth \- Data smoothing by convolution with Gaussian window.
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5
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6 .SH SYNTAX
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7 smooth [options] [file]
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8
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9 .SH DESCRIPTION
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10 Low-pass filter by convolving the input with a unit area Gaussian window
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11 in the time or frequency domain.
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12 The transform between domains uses the FFT.
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13
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14
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15 .SH OPTIONS
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16
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17 1. length
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18
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19 The amount of input to smooth in time units (ms or s) or samples (no units).
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20 Time units are converted to samples using the given `samplerate' option.
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21 The string "max" is recognised as the remainder of input.
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22
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23 2. domain
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24
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25 Select algorithm for smoothing.
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26 In the time domain ("domain=time") the discrete convolution formula is applied
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27 directly as a local averaging operation on the input with weights obtained
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28 by time-reversing and shifting a Gaussian window.
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29 In the frequency domain ("domain=frequency") the FFT of the whole input is
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30 multiplied by a Gaussian frequency response function (the FFT of the
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31 Gaussian window), and the result inverse FFT'd.
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32
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33 3. variance, range
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34
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35 The variance of the Gaussian window and its
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36 ordinal range in standard deviations either side of the mode.
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37 The window is assumed to be zero for all time outside the specified range.
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38 These parameters control the size of the window and consequently the amount
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39 of smoothing. The larger the variance, the more smoothing.
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40 The size of the window is given by:
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41
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42 .nf
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43 [ 2 * range * sqrt( variance ) ] samples + 1 sample
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44 .fi
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45
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46 The variance can be given with time units (ms or s) or samples (no units).
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47 Time units are converted to samples using the given `samplerate' option.
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48
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49 4. type
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50
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51 The input and output data type. Recognised types are "short" and "float".
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52
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53 .SH "SEE ALSO"
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54 options gauss filt1 conv
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55
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56 .SH COPYRIGHT
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57 .LP
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58 Copyright (c) Applied Psychology Unit, Medical Research Council, 1995
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59 .LP
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60 Permission to use, copy, modify, and distribute this software without fee
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61 is hereby granted for research purposes, provided that this copyright
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62 notice appears in all copies and in all supporting documentation, and that
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63 the software is not redistributed for any fee (except for a nominal
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64 shipping charge). Anyone wanting to incorporate all or part of this
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65 software in a commercial product must obtain a license from the Medical
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66 Research Council.
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67 .LP
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68 The MRC makes no representations about the suitability of this
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69 software for any purpose. It is provided "as is" without express or
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70 implied warranty.
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71 .LP
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72 THE MRC DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
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73 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
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74 THE A.P.U. BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES
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75 OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
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76 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
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77 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
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78 SOFTWARE.
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79
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