Solving for an x value using ppval

I have created a linear piecewise function using interp1 which works beautifully given the x value. Is there a way for which I could solve for an x value given the Y value? Example:

 hotStreamInterp = interp1(B,Hhotpt, 'linear', 'pp')';
 x = fsolve(480 = ppval(hotStreamInterp, x_unknown));

How could I properly write this? Thank you.

Answer 1

[Andrew Newell]

It depends - if x and y are 1-1, you can just switch them in the above two lines. In general, however, there is probably more than one x value for a given y value. Then you'll have to decide whether you want x from a particular interval or all the values of x. If you know where the extrema in x are, you could interpolate in the intervals between extrema.

[David Hagan]

Indeed they were 1-1...thank you very much.