Take only some values from one array

Hello everybody, I have an array of datas "x" and an array of time "t" that have some dimension like 30000x1, now I need just few values of this array x at some specific times.

I have this array of time called "t1" that is a long list of instants of time like 200x1 and I want to select the value of "x" corresponding only to the instants in "t1".

At the beginning I tryed to do as follows but Matlab says that this can't be done because the matrix dimensions must agree

  time= t==t1;
    x= x(time);

[dpb]

ismember

Answer 1

[J. Alex Lee]

you can't compare arrays of different lengths. a straightforward but cumbersome way is to cycle through each of your t1 and find the matches

x1 = nan(size(t1));
for i = 1:numel(t1)
    tcheck = t1(i)
    mask = (tcheck==t)
    if sum(mask)==1
        x1(i) = x(mask);
    end
end

Or you can use something like ismember to get the locations

[~,idx] = ismember(t1,t)
x1 = x(idx)

if your times in t1 aren't exactly the same as times in t, then you can use "ismembertol"