creating dummy variables
On Apr 20, 2013, at 3:56 PM, Eva Prieto Castro wrote:
Hi, Why do you write that dummy variables are not needed in R?. I would like you explain it.
I suppose you might want individual instruction, but Rhelp was established with certain principles (expressed in the Posting Guide), one of which is that persons posting to Rhelp should have made demonstrated effort on their own to study the offered documentation. You are not demonstrating that you have yet understood this principle.
David. > > Thanks, > > Eva > > --- El dom, 21/4/13, David Winsemius <dwinsemius at comcast.net> escribi?: > > De: David Winsemius <dwinsemius at comcast.net> > Asunto: Re: [R] creating dummy variables > Para: "Bert Gunter" <gunter.berton at gene.com> > CC: "r-help at R-project.org" <r-help at r-project.org>, "shyam basnet" <shyamabc2002 at yahoo.com> > Fecha: domingo, 21 de abril, 2013 00:38 > > > On Apr 20, 2013, at 2:03 PM, Bert Gunter wrote: > > > Dummy variables are not needed in R. > > > > Bert > > > > Bert is correct on this point, but if you what to know how the regression functions in R do this "behind the scenes" then you could always look at: > > ?model.matrix # where _some_ of the the automagical stuff happens > > > model.matrix( ~ crop, data=dat[,"crop", drop=FALSE]) > (Intercept) cropSWHE > 1 1 1 > 2 1 1 > 3 1 0 > 4 1 0 > 5 1 1 > 6 1 1 > 7 1 0 > 8 1 0 > attr(,"assign") > [1] 0 1 > attr(,"contrasts") > attr(,"contrasts")$crop > [1] "contr.treatment" > > > > > Sent from my iPhone -- please excuse typos. > > > > On Apr 20, 2013, at 11:23 AM, shyam basnet <shyamabc2002 at yahoo.com> wrote: > > > >> Hello R-users, > >> > >> The below is a snippet of my data: > >> > >> > >> fid crop year value > >> 5_1_1 SWHE 1995 171 > >> 5_1_1 SWHE 1997 696 > >> 5_1_1 BARL 1996 114 > >> 5_1_1 BARL 1997 344 > >> 5_2_2 SWHE 1995 120 > >> 5_2_2 SWHE 1996 511 > >> 5_2_2 BARL 1996 239 > >> 5_2_2 BARL 1997 349 > >> > >> Here, I want to create dummy variables with the names of the content of a column 'crop' in a way that the new variable 'SWHE' would receive a value of 1 if the column 'crop' contains 'SWHE' and 0 otherwise. So, I would have two new variables SWHE and BARL as below: > >> > >> > >> fid crop year value SWHE BARL > >> 5_1_1 SWHE 1995 171 1 0 > >> 5_1_1 SWHE 1997 696 1 0 > >> 5_1_1 BARL 1996 114 0 1 > >> 5_1_1 BARL 1997 344 0 1 > >> 5_2_2 SWHE 1995 120 1 0 > >> 5_2_2 SWHE 1996 511 1 0 > >> 5_2_2 BARL 1996 239 0 1 > >> 5_2_2 BARL 1997 349 0 1 > >> > >> > >> Cheers, > >> Shyam > >> Nepal > >> > > David Winsemius > Alameda, CA, USA > > ______________________________________________ > 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. > David Winsemius Alameda, CA, USA