comparison matlab/bmm/carfac/smooth1d.m @ 629:47c488dc7a01

Add missing matlab function smooth1d.m

+% Copyright 2010, Google, Inc.
+% Author Richard F. Lyon
+%
+% This Matlab file is part of an implementation of Lyon's cochlear model:
+% "Cascade of Asymmetric Resonators with Fast-Acting Compression"
+% to supplement Lyon's upcoming book "Human and Machine Hearing"
+%
+% Licensed under the Apache License, Version 2.0 (the "License");
+% you may not use this file except in compliance with the License.
+% You may obtain a copy of the License at
+%
+%     http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS,
+% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+% See the License for the specific language governing permissions and
+% limitations under the License.
+
+function cols = smooth1d(cols, scale)
+% smooth1d - Smooth the columns of the input.
+%
+% output = smooth1d(input, smoothing_factor)
+%
+% Smooth the columns of input using a one-pole smoothing filter, using the
+% provided smoothing factor.
+%
+% TODO(dross, dicklyon): make this code satisfy the google3 Matlab style.
+
+[nr, nc, nl] = size(cols);
+if nr == 1
+    if nl == 1
+        cols = cols';
+        [nr, nc, nl] = size(cols);
+    else
+        disp('error in shape passed to smooth1d')
+    end
+end
+
+if scale==0
+    polez = 0; % no smoothing at all
+    return;
+else
+    % this coefficient matches the curvature at DC of a discrete Gaussian:
+    t = scale^2;
+    polez = 1 + 1/t - sqrt((1+1/t)^2 - 1); % equiv. to the one below
+    % polez = 1 + 1/t - sqrt((2/t) + 1/t^2); % equiv. to the one above
+    % polez is Z position of real pole
+end
+
+[x, state] = filter(1-polez, [1, -polez], cols);
+cols = cols(end:-1:1,:);
+[cols, state] = filter(1-polez, [1, -polez], cols, state);
+cols = cols(end:-1:1,:);
+[cols, state] = filter(1-polez, [1, -polez], cols, state);
+
+return