[R] NAs spoil lowess smoothing

[Thomas Lumley]

On Thu, 28 Jan 1999, Stuart Luppescu wrote:

> Can anyone explain to me what this error message means, why I'm getting it, and
> how to fix it?
> 
>  lines(lowess(xdat, ydat, f=.5), col=3)
> Error: NAs in foreign function call (arg 1)


It means that in a call to .C or .Fortran there are missing values in the 
first argument. The call to .C is inside lowess(), and its first argument
is the x data. So you're getting it because there are NAs in xdat.

You can fix it by removing the NAs, eg
	good<-!(is.na(xdat) | is.na(ydat))
	lines(lowess(xdat[good],ydat[good],f=.5),col=3)

Refusing to handle NAs is the usual default behaviour of functions. Some
functions have na.action= arguments to control this, but lowess doesn't.


Thomas Lumley
Assistant Professor, Biostatistics
University of Washington, Seattle


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