Interpolate big array to match length of smaller array?

I am trying to do some array math, but my arrays are different sizes. I tried to interpolate the larger array, tau, (13795 x 1) to match the length of the smaller one, rho, (105 x 1). Neither data set is linear. I tried to do 1D interpolation with interp1(...) function but got the following error: "error using GriddedInterpolant The grid vectors do not define a grid of points that match the given values"

My end goal is to get the longer tau array to be (105 x 1).

[jonas]

How did you use interp1?

[Marissa Menzel]

new_data = interp1(rho,tau,?)

[Jake Gonzalez]

Are tau and rho different sizes because they are being sampled at different rates?

Correct me if I am wrong, but wouldn't you need to know the meaning of each values index in order to appropriately interpolate one data-set relative to the other?

[jonas]

rho and tau are functions of what? Some x vector I assume?

[Marissa Menzel]

They are density (rho) and wind stress (tau) that I am reading in from a data table file.

[jonas]

Measured over what? Over time? Over a geometry? Why are they different size?

Answer 1

[jonas]

You need an x vector for interp.

tau_new=interp1(X_tau,tau, X_rho)

tau_new is the interpolated vector

[Marissa Menzel]

I don't have an xshort and I can't just make one with linspace because it is non linear.

[jonas]

Can you upload and describe the data? You said you got the data from a table. What does the row number of the table represent? Is there a time associated with the values or perhaps a geometry? rho and tau must surely be functions of something right? Unless of course they are repeated measurements to get a measure of their distributions. In this case it is however senseless to interpolate.

Anyway, I am not supposed to figure it out.