change orientation of the label in matrix visual to 90 degrees

[nakagie]

In the matrix visual, I would like to put as many columns as possible. In order to do that, I would like to shorten the width of the columns. However, the word in the column label will be hidden almost when shotening the column width. So, I would like to change the orientation of the label in matrix visual to 90 degrees. 

Thank you very much.