[R] summary of categorical variables

[Chuck Cleland]

On 1/21/2008 8:08 AM, darteta001 at ikasle.ehu.es wrote:
> Dear list,
> 
> I have a data.frame with nine categorical variables (0,1,2 and NAs) 
> that I would like to get the number of events for each of them. I can 
> extract this using summary() for each variable at a time with the 
> as.factor()argument (otherwise it will get me the mean value):
> 
>> summary(as.factor(mydf[,3]))
>  0    1    2 NA's 
>  194   67    4    2
> 
> Trying to use apply() to get this for all the columns of the 
> data.frame I cannot use as.factor because it works with vectors and 
> not data.frames.

   How did you try to use apply()?  Try something like this:

df <- as.data.frame(matrix(sample(c(0,1,2,NA), 9*267, replace=TRUE), 
ncol=9))

apply(df, 2, function(x){summary(as.factor(x))})
      V1 V2 V3 V4 V5 V6 V7 V8 V9
0    70 69 75 72 71 75 66 58 66
1    70 67 64 64 64 55 62 65 72
2    63 60 56 79 57 73 75 69 67
NA's 64 71 72 52 75 64 64 75 62

> Can anyone help me? Maybe a for loop would be good in this case 
> instead, although I learnt that for loops are not recommended? 
> 
> Thanks in advance,
> 
> David
> 
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-- 
Chuck Cleland, Ph.D.
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