vmode.ffdf.rdFunction vmode returns the virtual storage mode of each ffdf column
# S3 method for class 'ffdf'
vmode(x, ...)a character vector with one element for each column
vmode(as.ffdf(data.frame(a=as.double(1:26), b=letters, stringsAsFactors = TRUE)))
#> a b
#> "double" "integer"
gc()
#> used (Mb) gc trigger (Mb) max used (Mb)
#> Ncells 1181591 63.2 1994352 106.6 1994352 106.6
#> Vcells 2205323 16.9 8790397 67.1 8790397 67.1