R help - Jan 2010 - Counting two factors at the same time

Hello.

I'm trying to count string data that correspond to a given
condition in two factors of the same length.

For example, I have one factor

[ 'A', 'B', 'A', 'C', 'B', 'D',
'B' ]

and another is 

[ '1', '2', '2', '3', '2', '2',
'3' ]

I'd like to count the occurences of 'B' and '2' (so in my
example, I should
get 2 as an answer, since there are 2 'B' that correspond to '2'
in the
other factor).

I tried doing it with loops (looping on one factor for 'B', looking for
the corresponding value in the second factor, and incrementing a counter
when the corresponding value is '2'), but I didn't succeed, and I
know it's
not the R-way.

Any hint or direction?

Thanks.

-- 
Fabrice DELENTE

Try this;
> f <- c( 'A', 'B', 'A', 'C', 'B',
'D', 'B')
> n <- c('1', '2', '2', '3', '2',
'2', '3')
> table(paste(f, n))
On Fri, Jan 22, 2010 at 4:51 PM, Fabrice DELENTE <fdelente at
mail.cpod.fr> wrote:
> Hello.
>
> I'm trying to count string data that correspond to a given
> condition in two factors of the same length.
>
> For example, I have one factor
>
> [ 'A', 'B', 'A', 'C', 'B',
'D', 'B' ]
>
> and another is
>
> [ '1', '2', '2', '3', '2',
'2', '3' ]
>
> I'd like to count the occurences of 'B' and '2' (so in
my example, I should
> get 2 as an answer, since there are 2 'B' that correspond to
'2' in the
> other factor).
>
> I tried doing it with loops (looping on one factor for 'B', looking
for
> the corresponding value in the second factor, and incrementing a counter
> when the corresponding value is '2'), but I didn't succeed, and
I know it's
> not the R-way.
>
> Any hint or direction?
>
> Thanks.
>
> --
> Fabrice DELENTE
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O

> Here's another R-way:
> 
> > lets<-factor(c( 'A', 'B', 'A', 'C',
'B', 'D', 'B'))
> # you did say they were factors, right?
> > nums <- factor(c('1', '2', '2',
'3', '2', '2', '3'))
> > lets=="B"
> [1] FALSE  TRUE FALSE FALSE  TRUE FALSE  TRUE
> > sum(lets=="B" & nums=="2")
> [1] 2
Thanks very much, it will save me :^)

As I am a beginner in R, I have a little trouble understanding factors. Can
they be used interchangeably with lists, or are they a different data-type?
Can I do on factors everything that I can do on lists?

Thanks again!

-- 
Fabrice DELENTE