Let's say I have a curve where the $y$-axis goes from $0$ to $1$, and the $x$-axis goes onto infinity.
I have three points: $[0,0]$, $[250 \, 000, 0.5]$, $[1 \, 000 \, 000, 0.9]$.
How could I interpolate these points to give me some multiplier to determine a $y$-value at a given $x$-point?