Interpolation error for one column increasing and one column decreasing

I am attempting to find an interpolation point from a matrix with one column having data in descending order and one column having data in ascending order. When I run the following line

h = interp1(Atmos2(:,1),Atmos2(:,2),1.1);

I get the error: Sample points must be unique and sorted in ascending order.

how do I alleviate this problem? Here is a sample of the data

Answer 1

[John D'Errico]

This is impossible to answer, since what you show is clearly not what you have.

The error that is given indicates the vector (x) is NOT a strictly increasing vector. But since you are interpolating density as a function of height, all I need do is look at the vector in column 2. It IS strictly increasoing. Therefore, you have not shown us a set of data that would cause that error.

Regardless, you need to insure that x (height) is an INCREASING vector.

[Brian N.]

How would I make x an increasing vector? Because density decreases with increasing altitude.