Question

For each of 100 data sets, I am using lm() to generate 7 different equations and would like to extract and compare the p-values and adjusted R-squared values.

Kindly assume that lm() is in fact the best regression technique possible for this scenario.

In searching the web I’ve found a number of useful examples for how to create a function that will extract this information and write it elsewhere, however, my code uses paste() to label each of the functions by the data source, and I can’t figure out how to include these unique pasted names in the function I create.

Here’s a mini-example:

temp <- data.frame(labels=rep(1:10),LogPre= rnorm(10))
temp$labels2<-temp$labels^2
testrun<-c("XX")

for (i in testrun)
{
  assign(paste(i,"test",sep=""),lm(temp$LogPre~temp$labels))
  assign(paste(i,"test2",sep=""),lm(temp$LogPre~temp$labels2))
}

I would then like to extract the coefficients of each equation

But the following doesn’t work:

summary(paste(i,"test",sep="")$coefficients)

and neither does this:

coef(summary(paste(i,"test",sep="")))

Both generating the error :$ operator is invalid for atomic vectors
EVEN THOUGH

summary(XXtest)$coefficients

and

coef(summary(XXtest))

work just fine.

How can I use paste() within summary() to allow me to do this for AAtest, AAtest2, ABtest, ABtest2, etc.

Thanks!

Answer 1

Hard to tell exactly what your purpose is, but some kind of apply loop may do what you want in a simpler way. Perhaps something like this?

temp <- data.frame(labels=rep(1:10),LogPre= rnorm(10))
temp$labels2<-temp$labels^2

testrun<-c("XX")
names(testrun) <- testrun

out <- lapply(testrun, function(i) {
  list(test1=lm(temp$LogPre~temp$labels),
       test2=lm(temp$LogPre~temp$labels2))
})

Then to get all the p-values for the slopes you could do:

> sapply(out, function(i) sapply(i, function(x) coef(summary(x))[2,4]))
                XX
test1 0.02392516
test2 0.02389790