MATLAB: Remove specific elements from array

Question 1

I have a 1x15 array, comprising of positive integers and negative integers. I wish to implement a MATLAB code which keeps all positive integers and skips the cells with negative contents.

I have tried the following:

X = [1 2 3 4 5 -10 1 -5 4 6 8 9 2 4 -2];
[r c]=size(X);
for i=1:r
    for j=1:c
        if X(i,j)<0
            X(i,j)=X(i,j+1)
        end
    end
end

The output should be X_new =[1 2 3 4 5 1 4 6 8 9 2 4] How do i do this?

Question 2

X = [1 2 3 4 5 -10 1 -5 4 6 8 9 2 4 -2]

Y = [5 3 8 9 4 5 6 7 4 7 9 5 2 1 4]

From Question 1, X_new = [1 2 3 4 5 1 4 6 8 9 2 4]. I need to delete the corresponding values in Y so that

Y_new = [5 3 8 9 4 6 4 7 9 5 2 1]. How do i perform this?