CODEWITHSUNDEEP
rmergedataframe
lojacobs
lojacobs

Reputation: 3

For loop and paste() to merge multiple dataframes in R

I have multiple identical dataframes: X1, X2, ..., X32

example of one dataframe:

> X1
    value
1 3300320

I would like to have juste one dataframe like that:

> XTotal
    value   X
1 3300320   1
2  345098   2
...
32  34355   32

I tried with a for loop and paste("X", i, sep=""), rbind, etc. but each time I got a list of string like that:

> listDF
1  "X1"
2  "X2"
...
32 "X32"

So, I can't call properly each dataframe to put their values in the XTotal dataframe...

I'm a little lost, any idea?

Thanks in advance!

Upvotes: 0

Views: 1939

Answers (1)

mnel
mnel

Reputation: 115392

Never grow an object in a loop. This is highly inefficient as it will copy the entire object every time.

to create a list of the data.frames use get and lapply or mget

dflist <-  mget(paste('X', 1:32), envir = parent.frame()) 
# also valid
# dflist <- lapply(paste('X', 1:32), get)

# to combine them
DFlist <- do.call('rbind', dflist)


# or, faster
library(data.table)
DFlist <- rbindlist(dflist)

If the data.frames do not have the same columns / order of columns use rbind.fill from plyr 

library(plyr)
DFlist <- rbind.fill(dflist)

There really isn't any need to create dflist explicity

Any of the following would also work

rbind.fill(mget(paste('X', 1:32), envir = parent.frame()))
rbindlist(mget(paste('X', 1:32), envir = parent.frame()))
do.call(rbind, mget(paste('X', 1:32), envir = parent.frame()))

Upvotes: 1

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