How to create a string of vector names in R that will then be able to be evaluated?

Question

In R, I currently have 100 dataframes, named df.1, ...,df.100. I would like to be able to rbind them but it is costly to write out:

rbind(df.1, df.2, etc)

So, I have tried:

rbind(eval(as.symbol(paste0("df.",1:84, collapse = ", "))))

However, this returns errors. Does anyone know how I can make the dataframes usable? thanks.

If you have any control over how these 100 dataframes are created in the first place, it's probably much easier to read them into a `list()` in the first place so you can access them using `df_list[["df1"]]`. — Marius, Jun 18 '18 at 01:19
I'd strongly recommend reading [How do I make a list of data frames](https://stackoverflow.com/a/24376207/903061). — Gregor Thomas, Jun 18 '18 at 01:33

G5W · Accepted Answer · 2018-06-18T12:00:00.070

1

You can rbind them one at a time in a loop.

df.1 = iris
df.2 = iris
df.3 = iris

DF = df.1
for(i in 2:3) {
    DF = rbind(DF, eval(as.symbol(paste("df", i, sep=".")))) }

edited Jun 18 '18 at 12:00

answered Jun 18 '18 at 01:26

G5W

did this need to be passed back into `DF` or does `rbind` concurrently save it? – user321627 Jun 18 '18 at 02:18
You are right. Need to store back in DF. Correcting answer. – G5W Jun 18 '18 at 11:59

score 1 · Answer 2 · answered Jun 18 '18 at 01:29

1

Using mget and then do.call or dplyr's bind_rows should work.

df.1 = iris[1:20,]
df.2 = iris[21:50,]

do.call("rbind",mget(paste0("df.",1:2)))

library(dplyr)
bind_rows(mget(paste0("df.",1:2)))

answered Jun 18 '18 at 01:29

Jul

It seems that the `do.call` function gives rownames that do not match. Is there a reason for that? – user321627 Jun 18 '18 at 01:54
2

@user321627 - rownames that don't match what? They are equivalent to `datasetname.rownumber`, presumably so you can match back to the original datasets if need be. – thelatemail Jun 18 '18 at 01:57

2 Answers2