# How can I interpolate rows in an array with a loop?

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Paola on 17 Aug 2021
Answered: Yazan on 18 Aug 2021
Hi I would like to interpolate rows of an array with a loop. I wrote this code but it doesn't work, can you help me to solve this problem? Thanks
for i=1:size(A,1)
vq=0.01
b(i,:)=interp1((1:length(A{i,:})),A{i,:},vq)
end
Dave B on 17 Aug 2021
What is A (i.e. type, shape)? what are you expecting in b?

Yazan on 18 Aug 2021
if A is an array, then Matlab will throw an error, as you are using curly braces for indexing.
Below is a demo on how to user interp1
t0 = 1:1:10;
% create a matrix contaning data sampled at step = 1;
t = repmat(t0, [3,1]);
x = (1:3)';
A = x.*t;
% assume you need to sample at a step = 0.5
tq = t0(1):0.5:t0(end);
% interpolate every row linearly and save results in B
B = nan(size(A,1), length(tq));
for j=1:size(A,1)
B(j, :) = interp1(t0, A(j,:), tq);
end
% plot one row of A and B
figure,
plot(tq, B(1,:)); hold on
plot(t0, A(1,:), 's'); grid minor
legend({'Interpolated data', 'Original data'})

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