How to use interp1 to stretch out smaller vector to size of larger vector?

So I have two vectors. The first vector has 1260 columns, and the second has 1778 columns. I want to take an average of these two vectors. It is being really hard to compare the two vectors since they are different lengths. How can I use the interp1 command to stretch out the smaller vector to the size of the larger vector? Any help would be really appreciated!!!