Re: [R] Create a new dataframe from an existing dataframe

From: Bert Gunter <gunter.berton_at_gene.com>
Date: Mon, 7 Jan 2008 11:55:14 -0800

?table

Bert Gunter
Genentech Nonclinical Statistics

-----Original Message-----
From: r-help-bounces_at_r-project.org [mailto:r-help-bounces_at_r-project.org] On Behalf Of Gang Chen
Sent: Monday, January 07, 2008 11:38 AM
To: Duncan Murdoch
Cc: R-Help
Subject: Re: [R] Create a new dataframe from an existing dataframe

Yes, I misstated it when I said that I would keep B and C. I want to collapse column A, but count the frequency of D as a new column in the new dataframe DF2 while collapsing A. The rows of columns B, C, and D of course would be reduced because of A collapsing.

For example, if dataframe DF is

A B C D
A1 B1 C1 D1
A1 B2 C1 D1
A1 B1 C1 D1
A1 B2 C2 D2
A2 B1 C1 D1
A1 B2 C2 D2
A1 B1 C2 D2
A2 B2 C1 D1
A1 B1 C2 D2

A2 B2 C1 D1
......

I would like to have a new dataframe DF2

B   C   D     FreqA
B1 C1 D1     6
B1 C1 D2     31
B1 C2 D1     8

B1 C2 D2 14
B2 C1 D1 12
B2 C1 D2 43
B2 C2 D1 23
B2 C2 D2 43

Thanks,
Gang

On Jan 7, 2008, at 2:06 PM, Duncan Murdoch wrote:

> On 1/7/2008 1:28 PM, Gang Chen wrote:
>> I have a dataframe DF with 4 columns (variables) A, B, C, and D,
>> and want to create a new dataframe DF2 by keeping B and C in DF
>> but counting the frequency of D while collapsing A. I tried
>> by(DF$D, list(DF$B, DF$C), FUN=summary)
>> but this is not exactly what I want. What is a good way to do it?
>
> I think you can't do that. If you want to keep B and C, then you
> can't reduce the number of rows, but "collapsing A" sounds like you
> want fewer rows.
>
> Perhaps if you posted a simple before and after example?
>
> Duncan Murdoch



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.

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. Received on Mon 07 Jan 2008 - 19:59:53 GMT

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.2.0, at Mon 07 Jan 2008 - 20:30:05 GMT.

Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help. Please read the posting guide before posting to the list.

list of date sections of archive