Matlab uses resample to complete resampling

fs1=10;
t1=0: 1/fs1 : 1;
x=t1;
y=resample(x, 3, 2);% The resampled signal is the number of elements of the original signal 3/2 times , That is to say, insert 0.5 Element of multiple quantity 
t2=(0: (length(y) - 1)) *2/(3 * fs1);
plot(t1, x, '*', t2, y, 'o', -0.5:0.01:1.5, -0.5:0.01:1.5, ':');
legend('original', 'resampled');
xlabel('Time');

You can see the resampled signal , Interpolation is not completely correct , Some inserted values deviate from the line .