R help - Aug 2008 - How to run a model 1000 times, while saving coefficients each time?

Hello,

We have written a program (below) to model the effect of a covariate on 
observed values of a response variable (using only 80% of the rows in 
our dataframe) and then use that model to calculate predicted values for 
the remaining 20% of the rows. Then, we compare the observed vs. 
predicted values using a linear model and inspect that model's 
coefficients and its R2 value.

We wish to run this program 1000 times, and to save the coefficients and 
R2 values into a separate dataframe called results.

We have a looping structure (also below) but we do not know how to save 
the coefficients and R2 values. We are missing some code (indicated)

Any assistance would be greatly appreciated.

Thanks,


library(sampling)

mall<-read.csv("mall.csv")

for (j in 1:1000) {

s<-srswor(2840,3550)
mall80<-mall[s==1,]
mall20<-mall[s==0,]
model1<-lm(count~habitat,data=mall80)
summary(model1)
mall20$predicted<-predict(model1,newdata=mall20)
model2<-lm(count~predicted,data=mall20)

MISSING CODE: SAVE MODEL COEFFICIENTS AND R2 VALUE TO A DATAFRAME CALLED 
RESULTS

}

?replicate

--
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
(801) 408-8111


> -----Original Message-----
> From: r-help-bounces at r-project.org
> [mailto:r-help-bounces at r-project.org] On Behalf Of Mark Na
> Sent: Monday, August 25, 2008 2:45 PM
> To: R-help at stat.math.ethz.ch
> Subject: [R] How to run a model 1000 times, while saving
> coefficients each time?
>
> Hello,
>
> We have written a program (below) to model the effect of a
> covariate on observed values of a response variable (using
> only 80% of the rows in our dataframe) and then use that
> model to calculate predicted values for the remaining 20% of
> the rows. Then, we compare the observed vs.
> predicted values using a linear model and inspect that
> model's coefficients and its R2 value.
>
> We wish to run this program 1000 times, and to save the
> coefficients and
> R2 values into a separate dataframe called results.
>
> We have a looping structure (also below) but we do not know
> how to save the coefficients and R2 values. We are missing
> some code (indicated)
>
> Any assistance would be greatly appreciated.
>
> Thanks,
>
>
> library(sampling)
>
> mall<-read.csv("mall.csv")
>
> for (j in 1:1000) {
>
> s<-srswor(2840,3550)
> mall80<-mall[s==1,]
> mall20<-mall[s==0,]
> model1<-lm(count~habitat,data=mall80)
> summary(model1)
> mall20$predicted<-predict(model1,newdata=mall20)
> model2<-lm(count~predicted,data=mall20)
>
> MISSING CODE: SAVE MODEL COEFFICIENTS AND R2 VALUE TO A
> DATAFRAME CALLED RESULTS
>
> }
>
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