MATLAB Answers

Take only some values from one array

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Carmine Schiavone
Carmine Schiavone on 16 Jul 2021
Commented: dpb on 16 Jul 2021
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);

Answers (1)

J. Alex Lee
J. Alex Lee on 16 Jul 2021
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"

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