Unable to create latex rules

[plukethep]

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I'm currently working on implementing latex column widths, which, when combined with alignments, are a little fiddly. I would like to use to align right a column, by declaring a new column type:

\newcolumntype{R}[1]{>{\raggedleft\let\newline\\\arraybackslash\hspace{0pt}}m{#1}}

I can inline this, but multiple tables would lead to multiple declarations, and I would would prefer to add the \newcolumn or \newcommand latex functions to the pre-body of the tex file just the once.

gt_latex_dependencies() in helper.R appears to do what I want, but it doesn't appear to be functioning. Am I missing something?