I have 3 csv files, I have three columns in all the three files( Maths, Physics and Chemistry) and marks of all the students. I created a loop to read all the files and saved in a dataframe as follows. In every file line numbers 1,2,4,5 need to be skipped.

```
files <- list.files(pattern = ".csv") 

for(i in 1:length(files)){
  data <- read.csv(files[i], header=F, skip=2) # by writing skip=2 I could only skip first two lines. 
  View(data)
  mathavg[i] <- sum(as.numeric(data$math), na.rm=T)/nrow(data)
}

result <- cbind(files,mathavg)
write.csv(result,"result_mathavg.csv")

```

I could not able to calculate the average of math column in all the three files.

Like this I need to calculate for all the three subjects across three files. 
any help????