I have a data set that I can turn into a curve(red). Which has mostly low values, but a number of points hockey-pucks to really high values.
I want to be able to map the red curve onto the green curve, which is a more gently sloping positive curve.
If I normalize the curves from 0-1, is there a way to look up into the red curve (curve U attribute), and get the corresponding Y value on the green curve (at the same U attribute position)?
Thanks

I believe you could do this with the primuv VEX function. Without having tested the code, it should be something like this, assuming you plug the red curve into the first input and the green into the second input of a wrangle:
vector pos = primuv(1, "P", 0, set(f@curveu, 0, 0));

Thanks, Digipiction.
I neglected to clarify the lookup mechanism I need:
For a point on the red curve's Y value, return the green curve's Y value with the same curveu index.
i.e. I need to look up: for a point on the red curve with a specific Y value, how do I get the corresponding curveu?

I'm sure there's a mathematical solution, but you could probably put a grid at the Y value so that it intersects the red curve, then do an intersection analysis or a boolean to create a point there and read its curveu.

Another way would be to resample the red curve heavily (give it a ton of points), then scale it to 0 on both X and Z so that it points straight up from the origin. Then find the closest point to your Y value:
int n = nearpoint(0, set(0, yValue, 0));
float curveu = point(0, "curveu", n);

I will give a try with Uvsample(), Uvdist()