[R] Loess fit

[David Winsemius]

On May 17, 2010, at 4:47 AM, Chintanu wrote:

> Hi,
>
> I wonder why my attempt to extend an existing loess fit to a new  
> data set is
> producing error. I was trying the following:
>
> dat = read.csv(choose.files())
> x = dat[,2]; y = dat[,1]
> x.sort = sort(x)

That is not needed, furthermore, you don't even use it.

> y.loess = loess(y~x, span=0.75)
>
> # For testing the above fit with a new dataset:
>
> test = read.csv(choose.files()) # test data
> new_x = test [,1]; new_y = test[,2]
> new_x.sort = sort(new_x)

That sort is not needed.

> predicted <- predict(y.loess, newdata=new_x.sort)
>
> Am I doing any mistake ? Please correct me.

How can we tell when the inputs to these functions are not offered?


>
> I could see that though the rest of the values of "predicted" looks  
> alright,
> however the first output of it is an NA !!

Perhaps outside the range of the loess function that was generated?

dat = matrix(rnorm(100), ncol=2); x = dat[,2]; y = dat[,1]
predicted <- predict(y.loess, newdata=x<-1:10 )
predicted
# [1] 0.1022490 0.2574732        NA        NA        NA         
NA        NA        NA
# [9]        NA        NA


>
> Many thanks,
>
> Chintanu
-- 

David Winsemius, MD
West Hartford, CT