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# Changing the frequency of an array does not work always

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Hi All

I have a time array , from which I first drop some elements, then change its frequency based on the input I give. the array is X in the code. what happens is that for some specific values , like reduction = 2 and freq = 1000 Hz if the original frequency of X was 512 Hz, the length of redt2 falls one element shorter than the original X array. how does this happen and what is the solution.

X is any time signal, 1D array with any length and frequency

reduction =2

X =X (1:reduction:numel(X));

redt1=[X];

rf= redt1(2)-redt1(1);

tend=redt1(numel(redt1));

freq= input(frequency)

dt= 1/freq

redt2= 0:dt:tend/rf/freq;

### Accepted Answer

Image Analyst
on 28 Nov 2020

In

freq= input(frequency)

what is frequency? Some string you defined to ask the user for the frequency? Please show how you defined it.

reduction = 2

X_Original = 1 : 1000;

whos X

samplingFreqOriginal = (X_Original(end) - X_Original(1)) / numel(X_Original)

X_Reduced = X_Original(1:reduction:numel(X_Original));

whos X

samplingFreqReduced = (X_Reduced(end) - X_Reduced(1)) / numel(X_Reduced) % Will be 2 times samplingFreqOriginal

% Not sure what anything after here is intended to do.

redt1 = X_Reduced;

rf = redt1(2) - redt1(1)

tend = redt1(numel(redt1))

frequency = 'Enter the frequency : ';

freq = input(frequency)

dt = 1 / freq

redt2 = 0:dt:tend/rf/freq;

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