[R] Recoding lists of categories of a variable

[MACDOUGALL Margaret]

Thank you for the valued suggestions in response to my query.

Margaret


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-----Original Message-----
From: Fox, John [mailto:jfox at mcmaster.ca] 
Sent: 10 October 2016 20:32
To: MACDOUGALL Margaret <Margaret.MacDougall at ed.ac.uk>
Cc: r-help at r-project.org
Subject: RE: Recoding lists of categories of a variable

Dear Margaret,

You've had one suggestion of an alternative for recoding variables, but in addition your code is in error (see below).

> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of 
> MACDOUGALL Margaret
> Sent: Monday, October 10, 2016 10:56 AM
> To: r-help at r-project.org
> Subject: [R] Recoding lists of categories of a variable
> 
> Hello
> 
> The R code
> mydata$newvar[oldvar = "topic1"] <- "parenttopic"

That should be

   mydata$newvar[oldvar == "topic1"] <- "parenttopic"

Moreover, the code assumes that oldvar is visible, which may not be the case if it lives in mydata and mydata isn't attach()ed.

Best,
 John

--------------------------------------
John Fox, Professor
McMaster University
Hamilton, Ontario, Canada
Web: socserv.mcmaster.ca/jfox

> 
> is intended to recode the category 'topic 1' of the old  varaible 
> 'oldvar' a new category label 'parenttopic' by defining the new 
> variable 'newvar'.
> 
> Is there a convenient way to edit this code to allow me to recode a 
> list of categories 'topic 1', 'topic 9' and 'topic 14', say, of the 
> the old variable 'oldvar' as 'parenttopic' by means of the new 
> variable 'newvar', while also mapping system missing values to system 
> missing values?
> 
> Thanks in advance
> 
> Best wishes
> Margaret