MATLAB: Please help: calculate average frequency of histogram

frequencyhistogram

Hello everyone,

I hope anyone could help me, I'm kinda new to Matlab.

I have two variables, speed and time. I would like to calculate mean duration of each speed interval.

For example:

In Speed interval between 2-4 mph (shown in yellow color), i have 4 speed data. The first data was last for 1-sec only, and the others were last for 3 sec. The mean duration of speed stability is 2 sec.

I really appreciate any help you give.

Thank you for your time.

Best Answer

Sp=[3 9 1 2 3 2.5 7.8 6.5 9.3 9.1]';
[n,b] = histc(Sp,0:2:10);
c = accumarray(b,(1:numel(Sp))',[],@(x){x});
ii = cellfun(@(z)numel(unique(diff(sort(z)))),c);
ii(~ii) = 1;
out = n(1:end-1)./ii;

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MATLAB: Count unique values in an array

If M is your cell array Try this,

c3=M(:,3)
[ii,jj,kk]=unique(c3)
f=histc(kk,1:numel(jj)); % Frequencies corresponding to ii
idx=f<100
idx1=ismember(c3,ii(idx))
M(idx1,:)=[]

MATLAB: How to replace for loop with vectorization

Hi,

You can eliminate the for loop by using the code below.

ii = [1 ; 2 ; 3 ; 1 ; 3 ; 4];
res = [-1 -1 1 ; -1 -1 1 ; -1 -1 1 ; 1 1 -1 ; 1 1 -1 ; -1 1 -1];
[x, y] = ndgrid(ii,1:size(res,2));
v=accumarray([x(:) y(:)],res(:));

But I would recommend to use the for loop if the size of the matrix is small.

In the above case

The elapsed time in the case of for loop is 0.000248 sec. Where as in the case of where for loop is eliminated the elapsed time is 0.000750 sec.

Hope this helps!

Best Answer

Related Solutions

MATLAB: Count unique values in an array

MATLAB: How to replace for loop with vectorization

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