LATEX: Hide column in table

Very nice. I forgot where I found it:

\def\ignore#1\endignore{}
\newcolumntype{I}{@{}>{\ignore}l<{\endignore}} %% blind out some colums


Now a table column with the letter "I" instead of c,r,l  will be hidden.
Of course there is a little extra space left

Needs the package:

\usepackage{array}