Inverse Interpolation

DESCRIPTION:

Use inverse linear interpolation to approximate the x value at which the function represented by xy is equal to yval.

USAGE:

NLSstClosestX(xy, yval) 

REQUIRED ARGUMENTS:

xy
a sortedXyData object
yval
the numeric value on the y scale to get close to

VALUE:

A single numeric value on the x scale.

EXAMPLES:

DNase.2 <- DNase[ DNase$Run == "2", ] 
DN.srt <- sortedXyData( expression(log(conc)), expression(density), DNase.2 ) 
NLSstClosestX( DN.srt, 1.0 )