Find the position of the first non-zero value in a matrix

Hello, I have the matrix of the image below and I want the position of the first non-zero value of the columns 2 until the end

i used the cumsum expression, it finds the first non-zero values:

out = mymatrix(cumsum(cumsum(mymatrix~=0)) == 1)

but when I do the find((mymatrix(cumsum(cumsum(mymatrix~=0)) == 1)) the result is not the desirable

Has someone any idea?

thanks in advance!

Answer 1

[KSSV]

A = rand(10) ; 
idx = randperm(10*10,80); 
A(idx) = 0 ; 
iwant = zeros(1,10) ; 
for i = 1:10
    iwant(i) = find(A(:,i),1) ;
end
iwant

[Giannis Nikolopoulos]

Hello, thanks you for your answer!!

I am trying this code in my matlab and sometimes it runs well but sometime the same exactly code has an error outcome. See the picture below:

additionally i didnt understant the use of randperm...

Sorry i am very new in Matlab :(

[KSSV]

Hi yes you are right, sometimes it will not run. When there is no non-zero element in a column the positon will be empty and in that case it will trhrow werror.

I am creating a demo random data for shwoing the solution to problem. To keep zeros randomly, I have used randperm. You can apply the solution to your data striaghtaway.

[Giannis Nikolopoulos]

Thanks for your answer!! finally worked!!

best