Question

I have some data.frames

dat1=read.table...
dat2=read.table...
dat3=read.table...

And I would to count the rows for each data set. So
the names are saved like this (cannot “change” it) vector=c(“dat1″,”dat2”,”dat3…)

p <- vector(numeric, length=1:length(dat))
counting <- function(x) {for (i in 1:x){
      p[i]<-nrow(dat[i])}
return(p)
}

This is not working because the input for nrow is a character, but i need integer(?) or?

Thx for help

Answer 1

You can use get for this, but be careful! Instead reading the tables at a list is the R-ish way:

file.names <- list.files()

dat <- lapply(file.names, read.table)

Then you have all the conveniences of lapply and the apply family at your disposal, e.g.:

lapply(dat, nrow)

The solution using get (also vector is a bad variable name since its a very important function):

lapply(vector, function(x) nrow(get(x)))

Your method fails since there is no object called dat to index into. The for loop could look like:

p = NULL
for(v in vector) {
  p <- c(p, nrow(get(v)))
}

But that technique is poor form for lotsa reasons…