count number values exceeds given threshold in moving window

I have time vs values plot. time =100. I want to select time 1 to 4 & then count how many values are exceeding 20. i.e. for time 1 to 4 values are 16 43 94 21 so 3 values are exceeding 20 so count should be 3. then want move window so time is 2 to 5 & count number of values exceeding 20. so last window would be 97 to 100. how to do it.

[Walter Roberson]

Duplicates http://www.mathworks.com/matlabcentral/answers/309511-how-to-count-no-of-elements-exceeding-given-threshold-value-in-selected-moving-window

Answer 1

[Fangjun Jiang]

M=100;
N=4;
A=randi(35,1,M);

B=A>20;
C=ones(N,M-N);
C(1,:)=1:(M-N);
C=cumsum(C);

D=sum(B(C));