[R] Using table to get frequencies of several factors at once
Pancho Mulongeni
p.mulongeni at namibia.pharmaccess.org
Mon Jan 14 09:17:10 CET 2013
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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