Matrix visual - how to sort by column

[Winniethewinner]

Hi everyone, 

I have a matrix visual like this, the default sorting option can only be done by rows: 

How can I sort volume by country as well? Thanks in advance. 

[lbendlin]

Have another column that implements the correct sort order for your category column. Then employ "Sort one column by another column".  Note:  This only works ascending.