MATLAB: I can’t use the function of decimate

MATLAB and Simulink Student Suite

Hi, I try an example of decimation stated in matlab. But I don't get the result as shown in the example. What should I do? Below shows the result that I run in my matlab. The first image is from the examaple, the second image is the result that I get.
t = 0:1/4e3:1;
x = sin(2*pi*30*t) + sin(2*pi*60*t);
y = decimate(x,4);
subplot(2,1,1)
stem(0:120,x(1:121),'filled','MarkerSize',3)
grid on
xlabel('Sample Number')
ylabel('Original')
subplot(2,1,2)
stem(0:30,y(1:31),'filled','MarkerSize',3)
grid on
xlabel('Sample Number')
ylabel('Decimated')

Best Answer

I get the same result as in the documentation (in R2020a).
First, what version of MATLAB are you using? The current online documentaion is for R2020a, however the decimate funciton could have changed over the years.
Second, run this line from a script or your Command Window: 
which decimate -all
The only result should be: 
C:\Program Files\MATLAB\R2020a\toolbox\signal\signal\decimate.m
or something similar for your version, if it is not R2020a.
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