[R] how do I draw such a barplot?

[Donatas G.]

Hi, 

I cannot figure out how to draw a certain plot: could someone help me out?

I have this data.frame from a survey
my.data

that looks like something like this:

   col1  col2  col3  col4
1     5     5     4     5
2     3     5     3     1
3     2     3     4     5
4     3     1     1     2
5     5     5     4     5
6     4     2     5     5
....


Each row represents a single questionnaire with someone giving his 
agreement/disagreement with a statement (each column is a statement) that is 
coded from 1 to 5.

I need to draw a barplot giving a visual representation showing differences 
between the five columns: Each bar should represent a single column, and 
should be divided into 5 sections, the thickness of each depending on the 
number of respondents who choose that particular answer.

How do I do that? All I have managed to do so far is to produce a barplot of a 
single column, and that - only with bars side by side...

-- 
Donatas Glodenis
http://dg.lapas.info