R help - Oct 2010 - How to iterate through different arguments?

If I have a model line = lm(y~x1) and I want to use a for loop to change the
number of explanatory variables, how would I do this?

So for example I want to store the model objects in a list.

model1 = lm(y~x1)
model2 = lm(y~x1+x2)
model3 = lm(y~x1+x2+x3)
model4 = lm(y~x1+x2+x3+x4)
model5 = lm(y~x1+x2+x3+x4+x5)...
model10. 

model_function = function(x){
for(i in 1:x) {
}
If x =1, then the list will only add model1. If x =2, then the list will add
both model1 and model2. If x=3, then the list will add model1 model 2 and
model3 and so on. How do I translate this into code?
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any solutions?
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There are several ways to do this.  The following is only one of the ways.
 One of the advantages of this approach is that it allows including both
continuous and categorical variables.

I'll demonstrate with the iris dataset.  Place your variables in a dataframe
with the y variable in the first column.  Then,

out<-list()
vars<-names(iris)

out[[1]]<-lm(Sepal.Length~1,data=iris)
for(k in 2:length(vars)){
 
out[[k]]<-update(out[[k-1]],as.formula(paste(".~.+",vars[k],sep="")))
  }

On Sun, Oct 3, 2010 at 4:29 PM, lord12 <trexinsd@yahoo.com> wrote:
>
> If I have a model line = lm(y~x1) and I want to use a for loop to change
> the
> number of explanatory variables, how would I do this?
>
> So for example I want to store the model objects in a list.
>
> model1 = lm(y~x1)
> model2 = lm(y~x1+x2)
> model3 = lm(y~x1+x2+x3)
> model4 = lm(y~x1+x2+x3+x4)
> model5 = lm(y~x1+x2+x3+x4+x5)...
> model10.
>
> model_function = function(x){
> for(i in 1:x) {
> }
> If x =1, then the list will only add model1. If x =2, then the list will
> add
> both model1 and model2. If x=3, then the list will add model1 model 2 and
> model3 and so on. How do I translate this into code?
> --
> View this message in context:
>
http://r.789695.n4.nabble.com/How-to-iterate-through-different-arguments-tp2953511p2953511.html
> Sent from the R help mailing list archive at Nabble.com.
>
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> R-help@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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On Sun, Oct 3, 2010 at 4:29 PM, lord12 <trexinsd at yahoo.com>
wrote:
>
> If I have a model line = lm(y~x1) and I want to use a for loop to change
the
> number of explanatory variables, how would I do this?
>
> So for example I want to store the model objects in a list.
>
> model1 = lm(y~x1)
> model2 = lm(y~x1+x2)
> model3 = lm(y~x1+x2+x3)
> model4 = lm(y~x1+x2+x3+x4)
> model5 = lm(y~x1+x2+x3+x4+x5)...
> model10.
>
> model_function = function(x){
> for(i in 1:x) {
> }
> If x =1, then the list will only add model1. If x =2, then the list will
add
> both model1 and model2. If x=3, then the list will add model1 model 2 and
> model3 and so on. How do I translate this into code?

Here are a couple of approaches.  The first one is simpler and may be
adequate.  The second has the advantage that it writes out the formula
in full, fo, which is shown in the output:

lapply(1:4, function(i) lm(y1 ~., anscombe[c(1:i, 5)]))

lapply(1:4, function(i) {
	fo <- formula(model.frame(y1 ~., anscombe[c(1:i, 5)]))
	do.call("lm", list(fo, quote(anscombe)))
})

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Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com

Thanks a lot! I have one other question,however. If I want to have two
garchFits,  garchFit(~aparch(1,1), data = sunspot.year) and
garchFit(~arma(2,1)+apaarch(1,1), data = sunspot.year), how do I automate
the creation of these models? 

for(k in 1:2)
{
  garchFit~...,data = sunspot.year), 
}

I am not sure what to put in the ...
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On Wed, Oct 6, 2010 at 10:16 AM, lord12 <trexinsd at yahoo.com>
wrote:
>
> Thanks a lot! I have one other question,however. If I want to have two
> garchFits, ?garchFit(~aparch(1,1), data = sunspot.year) and
> garchFit(~arma(2,1)+apaarch(1,1), data = sunspot.year), how do I automate
> the creation of these models?
>
> for(k in 1:2)
> {
> ?garchFit~...,data = sunspot.year),
> }
>
> I am not sure what to put in the ...


Set up a character vector of terms, Terms, such as

  Terms <- c("x1", "x2", "x3", "x4")

and then replace the fo<- line in my second solution with:

  fo <- as.formula(paste("y1", paste(Terms[1:k], collapse =
"+"), sep = "~"))


-- 
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com