Fix warnings

[klainfo]

==> R CMD INSTALL --no-multiarch --with-keep.source Rnalytica

• installing to library ‘/Library/Frameworks/R.framework/Versions/3.5/Resources/library’
• installing source package ‘Rnalytica’ ...
  ** R
  ** data
  *** moving datasets to lazyload DB
  ** inst
  ** byte-compile and prepare package for lazy loading
  Warning: replacing previous import ‘Hmisc::impute’ by ‘e1071::impute’ when loading ‘Rnalytica’
  Warning: replacing previous import ‘car::vif’ by ‘rms::vif’ when loading ‘Rnalytica’
  ** help
  *** installing help indices
  ** building package indices
  ** installing vignettes
  ** testing if installed package can be loaded
  Warning: replacing previous import ‘Hmisc::impute’ by ‘e1071::impute’ when loading ‘Rnalytica’
  Warning: replacing previous import ‘car::vif’ by ‘rms::vif’ when loading ‘Rnalytica’
• DONE (Rnalytica)

[patanamon]

I got an unclear error message.

> col = c('text_multinomial', 'text_gaussian')
> AutoSpearman(dataset = data, metrics = col)
Error in `$<-.data.frame`(`*tmp*`, "correlation", value = 100) : 
  replacement has 1 row, data has 0

I guess it is because there are only 2 metrics as an input. May need a more informative error message for a new user.