Combine exdf objects by columns or rows
cbind.exdf.RdCombines one or more exdf objects by the columns or rows of their
  main_data. For rbind, errors will occur if column names are not
  the same in all of the exdf objects, and if all units and categories
  are not identical.
Examples
# Make some simple exdf objects. 1 and 2 have the same number of rows but
# different columns, while 1 and 3 have the same columns but different rows.
simple_exdf_1 <- exdf(data.frame(A = 1), data.frame(A = 'au'), data.frame(A = 'ac'))
simple_exdf_2 <- exdf(data.frame(B = 2), data.frame(B = 'bu'), data.frame(B = 'bc'))
simple_exdf_3 <- exdf(data.frame(A = 2), data.frame(A = 'au'), data.frame(A = 'ac'))
cbind(simple_exdf_1) # will just return simple_exdf_1
#> 
#> Converting an `exdf` object to a `data.frame` before printing
#> 
#>   A [ac] (au)
#> 1           1
cbind(simple_exdf_1, simple_exdf_2)
#> 
#> Converting an `exdf` object to a `data.frame` before printing
#> 
#>   A [ac] (au) B [bc] (bu)
#> 1           1           2
rbind(simple_exdf_1) # will just return simple_exdf_1
#> 
#> Converting an `exdf` object to a `data.frame` before printing
#> 
#>   A [ac] (au)
#> 1           1
rbind(simple_exdf_1, simple_exdf_3)
#> 
#> Converting an `exdf` object to a `data.frame` before printing
#> 
#>   A [ac] (au)
#> 1           1
#> 2           2