[R] Newbie struggling with "factors"

[Tom Arnold]

I am processing some survey results, and my data are
being read in as "factors". I don't know how to
process these things in any way.

To start with, several of the survey questions are
mulit-choice check boxes on the original (web-based)
survey, as in "check all that apply".

These are encoded as numbers. For example, if the
survey has a question:
Which operating systems have you used? (Check all that
apply)
[ ]Windows
[ ]Macinotsh
[ ]Unix

...then the data exported for three different
responses might look like
;1;
;1,3;
;1,2,3;

...where ";" is the field delimiter. 
I use read.table to get the data in. I read all the
survey data into a table "n" and the field above is
called "OSUSE". When I query R about the field, it
tells me it is class "factor"

> class(n$OSUSE)
[1] "factor"
> mode(n$OSUSE)
[1] "numeric"

I'd like to be able to do some simple things like:
what is the most common item checked (1, 2, or 3?)
What is the average number of boxes checked?

But I can't find any way to manipulate this "factor"
field. What's the secret?

Thanks.

=====
Tom Arnold
Summit Media Partners
Visit our web site at http://www.summitmediapartners.com

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