R help - Oct 2014 - assigning a function within a loop

Hi,

I am trying to run several polynomial regressions on simulated data and produce
fitted values with the pol1, pol2 functions (predict produces not so nice plots,
see http://www.r-bloggers.com/polynomial-regression-techniques/). Below's a
simplified version of what I try to achieve. It seems that while assigning
within a loop does work, my assignment gets overwritten.

Any ideas - I suspect it is a basic mistake, my first post here...

Best,
Christoph

rm(list=ls())

# data generation
N=10
u = rnorm(N,0,.25)
x = sort(runif(N))
y = sin(2*pi*x)+u

# number of polynomials (just 2 for simplicity here)
degree = 2

plot(x,y)
for(i in 1:degree)
{
  nam <- paste("fit",i,sep = "")
  assign(nam, lm(y~poly(x,i,raw=TRUE))) # works nicely and I can access fit1,
fit2 later

  nam2 <- paste("pol",i,sep = "")
  assign(nam2, function(x)
matrix(x^rep(0:i,each=length(x)),ncol=i+1)%*%get(paste("fit",i,sep =
""))$coefficient[1:(i+1)])

  if(i==1) print(pol1(x)) # something different than pol2(x)
  #curve(get(paste("pol",i,sep = "")), col=20+i, lwd=2, add
= TRUE) # the ultimate goal
}

print(pol1(x)) # produces the same result as pol2(x), although it did not in the
loop
print(pol2(x))

	[[alternative HTML version deleted]]

Hi

instead of this paste/assign/get stuff use list for keeping cycle result

something like

nam <- vector("list", degree)

for (i in 1:degree) {
nam[[i]] <- lm(y~poly(x,i,raw=TRUE))
}

Cheers
Petr
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Hanck, Christoph
> Sent: Wednesday, October 29, 2014 1:17 PM
> To: r-help at r-project.org
> Subject: [R] assigning a function within a loop
>
> Hi,
>
> I am trying to run several polynomial regressions on simulated data and
> produce fitted values with the pol1, pol2 functions (predict produces
> not so nice plots, see http://www.r-bloggers.com/polynomial-regression-
> techniques/). Below's a simplified version of what I try to achieve. It
> seems that while assigning within a loop does work, my assignment gets
> overwritten.
>
> Any ideas - I suspect it is a basic mistake, my first post here...
>
> Best,
> Christoph
>
> rm(list=ls())
>
> # data generation
> N=10
> u = rnorm(N,0,.25)
> x = sort(runif(N))
> y = sin(2*pi*x)+u
>
> # number of polynomials (just 2 for simplicity here) degree = 2
>
> plot(x,y)
> for(i in 1:degree)
> {
>   nam <- paste("fit",i,sep = "")
>   assign(nam, lm(y~poly(x,i,raw=TRUE))) # works nicely and I can access
> fit1, fit2 later
>
>   nam2 <- paste("pol",i,sep = "")
>   assign(nam2, function(x)
>
matrix(x^rep(0:i,each=length(x)),ncol=i+1)%*%get(paste("fit",i,sep
> ""))$coefficient[1:(i+1)])
>
>   if(i==1) print(pol1(x)) # something different than pol2(x)
>   #curve(get(paste("pol",i,sep = "")), col=20+i, lwd=2,
add = TRUE) #
> the ultimate goal }
>
> print(pol1(x)) # produces the same result as pol2(x), although it did
> not in the loop
> print(pol2(x))
>
>       [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.
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