Finding index of closest value in an array of different dimension

Hello!

I have a large dataset of total pressure data and corresponding time in julian date. I have another dataset of different dimensions, with atmospheric pressure and time in julian date, with different observation times. My ultimate goal is to subtract atmospheric pressure at the closest time stamp from each observation of total pressure. I am aiming to do this by finding the index of the minimum difference between times, and subtracting the atmospheric pressure with that same index from the total pressure.

To find the index of the minimum difference between times, I have...

an array of times corresponding with total pressure, (2100x7647) - I call this array "x" in the below code.

an array of times corresponding with atmospheric pressure (2394x1) - I call this array "y" in the below code.

My matlab skills are poor to fair, but this is what I have so far:

[mlength mwidth] = size(y);

olength = length(x);

for ii = 1:mlength

for jj = 1:mwidth

for kk = 1:olength

[index(kk)] = min(abs(x(ii,jj)-y(kk,2)));

end

end

end

This is not working for me because

1. it is VERY inefficient
2. it is producing an array with different dimensions than I expected it to
3. the array is not filled with indeces corresponding to matching times but rather filled with times.

If someone could help me figure out what I am doing wrong I would be very grateful!

Thank you,

Rae

Answer 1

[Star Strider]

I am not certain that I understand what you want to do.

If you want to use the discrete timestamps, the ismembertol function might be worth trying.

An alternative approach is to interpolate, for example with the interp1 function.

[Rae Taylor-Burns]

Thanks! interp1 was what i needed. Sorry for the delayed response and thanks for your help!

[Star Strider]

As always, my pleasure!

MATLAB Answers was down for at least 8 hours today (at least for me), so I am only now seeing this.