No built-in interpolate function. For jointly increasing data try:

=PERCENTILE(B:B,PERCENTRANK(A:A,C1,308))

where C1 is the value to interpolate from the first two columns.

where columns A an

On 16 May, 06:30, barqqing wrote:
I have a set of x-y data, where each pair are non-integers (generally) and
the relationship is monotonic.

I want to be able to enter an x value, and have excel find a corresponding y
value based on the data.

The x value argument is unlikely to correspond exactly to an x in the
dataset, so I want the function to interpolate between the x values itfalls
between to find a y-value.

Is there such a function?