[R] Linear extrapolation; revision to earlier posting

[Frank E Harrell Jr]

The S-Plus approx function implements rule=3 (linear extrapolation), which is not implemented in R.  Has anyone extended approx to handle linear extrapolation?  

Regarding the use of approx for "closest matching" in my post from last week, you need to add ties=function(x)x[1], e.g.

round(approx(c(1,3,5,2,4,2,4),1:7,xout=c(1,3,5,2,4,2,4),rule=2,
       ties=function(x)x[1])$y)

-- 
Frank E Harrell Jr              Prof. of Biostatistics & Statistics
Div. of Biostatistics & Epidem. Dept. of Health Evaluation Sciences
U. Virginia School of Medicine  http://hesweb1.med.virginia.edu/biostat
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