how to use try()
On Mon, 9 Feb 2004, r.ghezzo wrote:
Hello, I have a program with this section:
..
for(i in 1:20){
lo <- nls(y~y0+a/(1+(x/x0)^b),start=list(y0=0.1,a=a0,x0=x00,b=-8.1))
beta[i] <- lo$m$getPars()[4]
}
..
If the fit works this is OK but if the fit fails, the whole program
fails so:
..
for(i in 1:20){
try(lo <-
nls(y~y0+a/(1+(x/x0)^b),start=list(y0=0.1,a=a0,x0=x00,b=-8.1)))
beta[i] <- lo$m$getPars()[4]
}
..
but the try catches the error in nls and beta[i] gets assigned beta[i-1]
from the previous loop. This is bad but no so bad as it can be checked,
You want either both assignments inside the try()
try({
lo<-nls(....)
beta[i]<-lo$m$getPars(4)
})
or both outside
lo<- try(nls(....))
if (inherits(lo,"try-error")) beta[i]<-NA else beta[i]<-lo$m$getPars()[4]
-thomas