通过动态选择名称来组合多个数据框

Question

I received a script that generates a bunch of objects. I want to combine multiple dataframes using bind_rows. I am able to choose the correct objects using grep but I am not able to pass those object names as argument to bind_rows.

For example, I want to select the objects that start with df and pass those to bind_rows. In the example below I expect to have a dataframe named data which have the dataframe mtcars 3 times.

df1 <- mtcars
df2 <- mtcars
df3 <- mtcars
notdf4 <- mtcars
dfx <- ls()[grep("^df", ls())]
data <- bind_rows(eval(parse(text = dfx)))

Answer 1

The suggestion to use mget makes sense, although it returns a list so you would need to use do.call to execute an `rbind operation.

str( do.call( rbind, mget(ls( patt="^df.") ) )  )
'data.frame':   96 obs. of  11 variables:
 $ mpg : num  21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
 $ cyl : num  6 6 4 6 8 6 8 4 4 6 ...
 $ disp: num  160 160 108 258 360 ...
 $ hp  : num  110 110 93 110 175 105 245 62 95 123 ...
 $ drat: num  3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ...
 $ wt  : num  2.62 2.88 2.32 3.21 3.44 ...
 $ qsec: num  16.5 17 18.6 19.4 17 ...
 $ vs  : num  0 0 1 1 0 1 0 1 1 1 ...
 $ am  : num  1 1 1 0 0 0 0 0 0 0 ...
 $ gear: num  4 4 4 3 3 3 3 4 4 4 ...
 $ carb: num  4 4 1 1 2 1 4 2 2 4 ...

I think using mget and do.call (rather than will have a lower chance of offending people like me who might be called R purists. I chose to use the "pattern" argument to ls as cleaner than first getting all the workspace names and then selecting from them with grep.