Vectorize polyphase filter operation

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Shannon Cherry 2020-4-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/517807-vectorize-polyphase-filter-operation

Hi, I have implemented a matlab code for polyphase filter. Is there any way I could vectorize/optimize this code by avoiding nested for loops?

clc;clear;close all;
% Input parameters
input = [2 4 6];
upSamplingFactor = 3;
% filter coefficients
h = 1:9;
%% Polyphase filter without any inbuilt libraries
% Y(n) = sum(X(i)*h(n-Li); where L = upFactor
outputLen = numel(input)*upSamplingFactor;
output = zeros(1,outputLen);
for outIndex = 1:outputLen
   nextIndex = 0;
   for loopIndex = 0:upSamplingFactor:outIndex-1
     output(outIndex) = output(outIndex) + input(nextIndex+1)*h(outIndex-upSamplingFactor*nextIndex);
     nextIndex = nextIndex + 1;
   end
end