how to create a matrix from a loop using other matrix

c = [1
    2
    3
    4
    5
    6
    7
    8
    9
    10];

d = [1
    0
    0
    -1
    0
    0
    1
    0
    1
    1];

i = zeros(numel(d),1);
for i1 = 2:numel(i)
    if d(i1) == 1
        i(i1) = c(i1);
    elseif d(i1) == -1
        i(i1) = c(i1)*-1;
    else
        i(i1) = i(i1-1);
    end
end

[Rik]

So, what is your question? I only see some unformated code.

Have a read here and here. It will greatly improve your chances of getting an answer.

[dpb]

How to vectorize I presume is the ?

? to OP, though...your loop will only set the value to succeeding for those after the first as it is sequential and passes by the first element. Is this intended or is it intended that all elements in i end up nonzero in the end?

Also, while I don't have an issue with using i as a loop index or temporary in defiance of the builtin definition, I would recommend to NOT use it as a result variable array as here. Pick another variable name for the real case.

Answer 1

[Andrei Bobrov]

out = d.*c;
t = d ~= 0;
cc = out(t);
out = cc(cumsum(t));