using find function and stor the filtered data in a Matrix

Hello,

I have two columns of data. frequency and H. Now I want to find H values, which the respective frequency values belongs to predefined classess and stor them in a matrix. per say, f = (1.3; 1.4; 2.1; 2.5; 2.7; 2.8; 3.4) and H = (5;6;7;3;2;4;9). Now I want to find which H values falls in frequency classes of (1-2), (2-3), (3-4) and store them in a matrix (may be row sizes are unequal, make it equal size with rest of the elements being set to zeros). Since I have so many classes, I am hoping to do so using a for loop and find function. (expected answer is something like below with columns are representing frequency classes of (1-2), (2-3), (3-4) in order.

[5 7 9

6 3 0

0 2 0

0 4 0]

Answer 1

[Dyuman Joshi]

Assuming the ranges are [1,2), [2,3) ...

f = [1.3; 1.4; 2.1; 2.5; 2.7; 2.8; 3.4];
H = [5;6;7;3;2;4;9];
arr = floor(f);
[~,m]=mode(arr);
%pre-allocation
out = zeros(m,max(arr));
%generalised approach instead of 1:max(arr)
for k = unique(arr)'
    z = arr==k;
    out(1:nnz(z),k)=H(z);
end
out

out = 4×3

5 7 9 6 3 0 0 2 0 0 4 0

[Voss]

Note that using mode(arr) for determining the number of rows to pre-allocate in the output matrix is not correct in general; it should be nnz(arr==mode(arr)) to get the number of times the mode of arr appears in arr, rather than just the mode of arr itself.

[Dyuman Joshi]

Thanks for pointing it out, Voss. I have edited my code to rectify the mistake.

[Tharindu]

Thanks Joshi and Voss! I figured out the logic behind. Great help. Thanks to both of you!!