Select and remove/replace values in matrix

My question is to check each row for the same numbers (in this case 1 or 0, we leave the 0s unchanged in the matrix), and replace any 1 in the row with 0 except the last value of 1

Y = [0 1 1 0 1 0;
    0 0 0 1 0 1;
    1 0 1 0 1 0; ]

The end result I should get is

X = [0 0 0 0 1 0;
     0 0 0 0 0 1;
     0 0 0 0 1 0;]

Another similar question would be to remover the first/second (sometimes even third) number in the row leaving the last 2 numbers unchanged.

Y = [1 2 4 0 0 0;
     2 5 0 0 0 0;
     3 4 5 6 0 0;]

The end result I should get is

X = [0 2 4 0 0 0;
     2 5 0 0 0 0;
     0 0 5 6 0 0;]

Answer 1

[Guillaume]

One way:

nelems = 2;  %number of elements to keep
X = (cumsum(Y>0, 2, 'reverse') < nelems+1) .* Y

[JL]

I have tried it but it gives me the below answer:

X =

0 0 1 0 1 0

0 0 0 1 0 1

0 0 1 0 1 0

I'm trying to get something like this below:

X =

0 0 0 0 1 0

0 0 0 0 0 1

0 0 0 0 1 0

[JL]

It is working for both problems! Thank you very much - i just checked again!

[JL]

I have another follow up question please. If I have introduced Z

Z = [2;
     0;
     15;]

to this matrix

X =
    [ 0     0     1     0     1     0;
     0     0     0     1     0     1;
     0     0     1     0     1     0;]

where we only replace 1 with 0 if Z is >0 with that

Y = 
    [ 0     0     0     0     1     0;
     0     0     0     1     0     1;
     0     0    0     0     1     0;]

[Guillaume]

Probably, the simplest is to use the same as before, then reinsert the original rows when Z is 0:

nelems = 1;  %number of elements to keep
Y = (cumsum(X>0, 2, 'reverse') < nelems+1) .* X;
Y(Z == 0, :) = X(Z == 0, :)

[JL]

Thank you, it is working!

[JL]

Hi Guillaumen, I have another intetesting problem, was wondering if you are interested to take a look - here is the link to the question https://uk.mathworks.com/matlabcentral/answers/475460-sharing-values-of-elements-in-a-matrix