[R] Creating new variables in R

[Erich Neuwirth]

data <- within(data,variable3=pmax(variable1,variable2))
also should work if your variables are numeric.

using dplyr and magrittr (which I recommend to all my students)
it could be

library(dplyr)
library(magrittr)
data %<>% mutate(variable3=pmax(variable1,variable2))



> On 26 Oct 2015, at 12:53, PIKAL Petr <petr.pikal at precheza.cz> wrote:
> 
> Hi
> 
>> -----Original Message-----
>> From: R-help [mailto:r-help-bounces at r-project.org <mailto:r-help-bounces at r-project.org>] On Behalf Of Duncan
>> Murdoch
>> Sent: Monday, October 26, 2015 11:58 AM
>> To: Lorenz, Jennifer; r-help at r-project.org <mailto:r-help at r-project.org>
>> Subject: Re: [R] Creating new variables in R
>> 
>> On 26/10/2015 6:24 AM, Lorenz, Jennifer wrote:
>>> Hi,
>>> 
>>> I  have a question regarding the creation of new variables on the
>> basis of existing ones in R.
>>> 
>>> I have two variables containing information on parents' educational
>> degree (e.g. 1 'high school degree', 2 'college degree', etc.). I would
>> like to create a new variable for 'parents' highest educational
>> degree', i.e. if variable1 (father's degree) is higher than variable2
>> (mother's degree) than the new variable (variable3) should take on the
>> value of variable1, if not, than variable3 should take on the value of
>> variable2.
>>> 
>>> I usually use SPSS for data manipulation, there I would code
>> variable3 as follows:
>>> COMPUTE variable3= 0.
>>> IF variable1 > variable2 variable3= variable1.
>>> IF variable1 <= variable2 variable3= variable2.
>>> 
>>> The closest I came to that in R was with this code:
>>> data$variable3 <- 0
>>> data$variable3[data$variable1 > data$variable2]<-data$variable1
>>> data$variable3[data$variable1 <= data$variable2]<-data$variable2
>>> 
>>> I also tried:
>>> data$variable3 <- ifelse(data$variable1 > data$variable2),
>>> data$variable1, data$variable2)
>>> 
>>> Both didn't work.
> 
> The ifelse version should work. Are you sure that variable 1 and 2 are numeric?.
> 
> What is a result of str(data)?
> 
> Cheers
> Petr
> 
>>> 
>>> I am not sure if my post is at all understandable (this is my first
>> time posting on R-help), but I am really hoping for some advice!
>> 
>> This is a good place to use the ifelse() function:
>> 
>> data$variable3 <- ifelse(data$variable1 > data$variable2,
>>                         data$variable1, data$variable2)
>> 
>> Duncan Murdoch
>> 
>> ______________________________________________
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>> guide.html
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