How to change values in an array based on certain rules?

I have an array and I want to change it so that all entries are zero except each first appearing 1 and -1.

But also, the first nonzero entry needs to be a +1.

I've been trying to use a for loop with if statements to accomplish this, but I can't figure out what rules would be used.

The result should be this:

x = [-1 0 0 1 1 0 1 -1 -1 -1 0 1 1 1 0 0 1 -1 0 0 -1 1 0 0 -1 0] %  change this array to...
xx= [ 0 0 0 1 0 0 0 -1  0  0 0 1 0 0 0 0 0 -1 0 0  0 1 0 0 -1 0] % this
%     ^     ^        ^         ^            ^        ^      ^
%     |  % all of these are the only ones that remain - they alternate between 1 and -1
%     |
% and here the -1 from x is eliminated because there is no preceding +1

% the array x is randomly generated to be a -1, 0, or a 1

Any insight would be appreciated... thank you

Answer 1

[Yasasvi Harish Kumar]

Hi,

Something like this should fix your problem.

f = 1;
for  i = 1:length(x)
    if x(i) == f
        xx(i) = f;
        f = -f;
    else
        xx(i) = 0;
    end
end

Regards