[R] Using table to get frequencies of several factors at once

[Pancho Mulongeni]

Yes thank you, that worked.

-----Original Message-----
From: John Kane [mailto:jrkrideau at inbox.com] 
Sent: Friday, January 11, 2013 4:23 PM
To: Pancho Mulongeni; R help
Subject: RE: [R] Using table to get frequencies of several factors at once

Does something like this do what you want?  It returns a list of tables

md  <-  data.frame((matrix(sample(1:5, 100, replace = TRUE),nrow= 10)))
  str(md)
  apply(md, 2, table)

John Kane
Kingston ON Canada


> -----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 Fouché Street
> Windhoek West
> Windhoek
> Namibia
> 
> Tel:   +264 61 419 000
> Fax:  +264 61 419 001/2
> Mob: +264 81 4456 286
> 
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