将data.frame名称传递给函数R

Question

I have .RData files stored and I would like to do a function that load the .RData and then use a data.frame named df that was in the .RData, but the name of the data.frame is a parameter of the function, like this:

test <-function(rdat,df)
{
load(rdat)
df <-with(df, subset(df, status=='A'))
test1(df)
}

test1 <-function(df)
{
df$new <- mean(df$old)
}

I don't realize how to convert a string with the name of a data.frame in a data.frame object to use, I can't pass the data.frame itself because it doesn't exist. Maybe there is a way to search in the environment for the data.frame named df.

Thanks!

Answer 1

You need to use the get function:

As an example of how get works try this:

mat <- matrix(letters, ncol=2)
get('mat')
 #    [,1] [,2]
 #[1,] "a"  "n" 
 #[2,] "b"  "o" 
 #[3,] "c"  "p" 
 #[4,] "d"  "q" 
 #[5,] "e"  "r" 
 #...and so on

So your function could be like this:

test <-function(rdat,df)
{
load(rdat)
#get will give you the data.frame from a string
df <- get(df)
#also you do not need 'with' with subset because subset uses NSE anyway
#and also using subset inside of functions is error prone because of NSE
#use simple subsetting which is faster, too
df <- df[df$status=='A',]
test1(df)
}