Using table to get frequencies of several factors at once

-----Original Message-----
From: p.mulongeni at namibia.pharmaccess.org
Sent: Fri, 11 Jan 2013 11:17:42 +0000
To: r-help at r-project.org
Subject: [R] Using table to get frequencies of several factors at once

Hi, I have a dataframe with n columns, but I am only looking at five 
of them. And lots of rows, over 700.
So I would like to find frequencies for each of the numeric columns
(variables) using the table function. However, is there a fast way to 
produce a frequency table where the 5 rows represent the 5 numeric 
variables and the columns refer to the values (levels) of the 
respective numeric variables, which in this case are 0 and 1.
The only way I have figured it out is via a for loop:
m<-seq(218,222,1) #these are columns of the variables in the larger 
dataframe tm<-m[1:5] #I need this for the for loop
l.tm<-length(tm)
B<-matrix(nrow=l.tm,ncol=2)  #the matrix to hold the freqs for (p in 
1:l.tm) { var.num<-m[p]
B[p,]<-table(DATA[,var.num])
}

B

     [,1] [,2]
[1,]  697    9
[2,]  512  194
[3,]  604  102
[4,]  700    6
[5,]  706  706
So the rows represent my five variables (columns) that occupy columns 
218 through 222 in the DATA dataframe.
So the second column represents my frequencies of the value 1, which 
is what I am interested in. The last row has a double entry, because 
there was only one value, 0, with a freq of 706 and so R duplicated in 
the two columns, but that's ok, I can just ignore it.

So is there are better way to do this? Is there a way to use the so 
called tapply function? I struggle to understand the help doc for 
this.function.


Pancho Mulongeni
Research Assistant
PharmAccess Foundation
1 Fouch? Street
Windhoek West
Windhoek
Namibia

Tel:?? +264 61 419 000
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