Counter in Variable Selection - r

Question

I am running the following code, which is working fine:
model <- NULL
summary <- NULL
stepwise <- NULL
for (i in 1:100){
model[[i]] <- lm(r[[i]]~x1[[i]]+x2[[i]]+x3[[i]]+noise1[[i]]+noise2[[i]]+noise3[[i]]+noise4[[i]]+noise5[[i]]+noise6[[i]]+noise7[[i]])
summary[[i]] <- summary(model[[i]])$coefficients
stepwise[[i]] <- step(model[[i]], direction="both")$coefficients
}
I wanted to set up a counter to keep track of the variables that are stored in the stepwise list. I want a count of how many times each variable (x1, x2, x3, noise1, noise2, noise3, noise4, noise5, noise6, noise7) occurs. I was thinking of something like this
createCounter <- function(VALUE){
for (i in 1:100){
output <- VALUE <- VALUE+i
return(output)
}
}
but I don't know how to fine-tune it so that R understands to count a value if the stepwise list contains the particular variable. Any help would be appreciated.

Answer 1

well, the step()$coefficients returns a named vector of the coefficients. While the values contain the actual coefficients, the names on the vector store the actual names of the variables. So you can extract and count all the variable names from all the 100 models with
table(unlist(lapply(stepwise, function(x) names(x))))