Find elemet which are satisfy given condition

hello to everyone! I have a task, where i need to find in column (x) with 100 numbers, such values which are less or equal than 400. And write all these values in new created matrix x1. When I run this code - new matrix from zeros is created, but it doesn't contain any numbers. What could be the reason? Will appreciate your help!

x1=zeros(100,1);
for i=1:100
    if x(i)<=400
        x1(i)=x(i);
    end
end

[Dyuman Joshi]

Your code looks good. What is the value of variable x?

You can assign the values via indexing, which is more efficient than loop

x = randi(750,10,1)

x = 10×1

386 629 86 13 279 497 411 409 239 458

x1 = zeros(size(x));
idx = x<=400;
x1(idx) = x(idx)

x1 = 10×1

386 0 86 13 279 0 0 0 239 0

Answer 1

[Jan]

Your code is working:

x  = [1, 401, 400, 500, 10, 300];
x1 = zeros(numel(x), 1);
for i = 1:numel(x)
    if x(i) <= 400
        x1(i) = x(i);
    end
end
x1.'

ans = 1×6

1 0 400 0 10 300

You can omit the zeros also:

x  = [1, 401, 400, 500, 10, 300];
x1 = zeros(numel(x), 1);
k  = 0;   % Another counter
for i = 1:numel(x)
    if x(i) <= 400
        k = k + 1;
        x1(k) = x(i);
    end
end
x1 = x1(1:k);  % Crop unused elements

A more Matlab'ish way is to omit the loop:

x1 = x(x <= 400)    % Logical indexing