how to design a moving window? which has to move sample by sample in simulink

hi,

i have converted analog signal to digital using ADC, now i have to apply a moving window to this incoming digital signal and the width of the window is 1 cycle i.e 80 samples.... please help me regarding this

[Fangjun Jiang]

Assume you have 1000 samples of data, you want to apply a rolling window of 80 samples at a time, what type of processing do you want to do? average, filtering? Please specify.

Also, consider Matlab. Depending on your task, sometimes Matlab is more suitable than Simulink for the job.

Answer 1

[Fangjun Jiang]

Here is a quick and easy way to do it in Matlab.

a=0:0.1:100;
WindowWidth=80;
b=sin(a);
c=abs(b);
d=zeros(size(b));
d(1)=sum(c(1:WindowWidth));
for i=2:(numel(a)-WindowWidth+1)
    d(i)=d(i-1)-c(i-1)+c(WindowWidth+i-1);
end
figure(1);plot(b);
figure(2);plot(d);

[harish bharadwaj]

thnks i will try this

Answer 2

[Sean de Wolski]

doc conv

Edit for Fangjun:

isclose = @(x,y)isequal(size(x),size(y))&&all(abs(x-y)<10^-5)
cway = conv(c,ones(1,80),'valid'); %other shapes if wanted (doc conv)
isclose(d(1:end-79),cway) %throw away your end 80 zeros

ans =
   1

[Fangjun Jiang]

Thanks, Sean. Will check later. I am off Matlab now.

[Fangjun Jiang]

Sean, not sure how to use the conv() function. Harish asked me in an email that he wanted to calculate the sum of the absolute value of all the samples in a rolling window. The rolling window always contains 80 samples. I modified my code above to use sum() just once instead of using sum() in the loop. The point is to show him that it is easier to do it in Matlab rather than in Simulink. It's probably not that important whether the code is most efficient or most concise. But I would love to know if there is a built-in function to calculate the rolling sum of a vector.

[Sean de Wolski]

conv!

[Fangjun Jiang]

Thanks, Sean!

@Harish, consider using the conv() function if you want the sum has a nice ramp up and ramp down.