I need some help here.

I have some data in which every entry can take one or more levels of a categorical variable. for example, I have a category with 3 levels:

entry   category
1       A, B, C
2       B
3       C, A, B

How should I organized it into a file in order to easily let R discriminate among levels in order to do my analysis. Something like this:

Categories     entries    other_results
A              2          ~
B              3          ~
C              2          ~ 

I thought about doing a comma separated list, as shown in the example 1. But then what should I do in R in order to transform those string into categories?

thanks!

I need some help here.

I have some data in which every entry can take one or more levels of a categorical variable. for example, I have a category with 3 levels:

entry   category
1       A, B, C
2       B
3       C, A, B

How should I organized it into a file in order to easily let R discriminate among levels in order to do my analysis. Something like this:

Categories     entries    other_results
A              2          ~
B              3          ~
C              2          ~ 

I thought about doing a comma separated list, as shown in the example 1. But then what should I do in R in order to transform those string into categories?

CLARIFICATION: I'd like to avoid creating a column for every level. This variable has many levels and many other variables are already present. This would make the file uselessly big and not readable easily by humans.

thanks!