[R] to create a new variable based on values in other variables

[Thierry Onkelinx]

Dear Ding,

It seems that you are looking for the ifelse() function. Clear use of
pmax() and pmin() reduces the number of if statements.

m1 <- c(12, 23, 22, 23)
m2 <- c(23, 23, 3, 5)

Ravg <- ifelse(
  pmax(m1, m2) == 23,
  pmin(m1, m2),
  (m1 + m2) / 2
)

Best regards,

ir. Thierry Onkelinx
Statisticus / Statistician

Vlaamse Overheid / Government of Flanders
INSTITUUT VOOR NATUUR- EN BOSONDERZOEK / RESEARCH INSTITUTE FOR NATURE AND
FOREST
Team Biometrie & Kwaliteitszorg / Team Biometrics & Quality Assurance
thierry.onkelinx using inbo.be
Havenlaan 88 bus 73, 1000 Brussel
www.inbo.be

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Op di 7 apr. 2020 om 20:35 schreef Yuan Chun Ding <ycding using coh.org>:

> Hi R users,
>
>
> I want to create a new variable, Ravg, in data frame tem2 based on values
> of two other variables m1 and m2.
>
> the condition:
>
> if m1 = 23 and m2 =23 then Ravg =23;
> else if m1 != 23 and m2=23 then Ravg =m1;
> else if m1 =23 and m2 !=23 then Ravg=m2;
> else Ravg=average of m1 and m2;
>
> the Ravg variable should be  same as  m3 variable in the following small
> example.
>
> my R code did not generate errors but not generate a new variable.
>
> Ravg <- "rare_allele"
>   tem2 <-data.frame(m1=c(12, 23, 22, 23), m2=c(23, 23, 3, 5), m3 =c(12,
> 23, 12.5, 5))
>   for (r in 1:nrow(tem2)) {
>   if (tem2$m1[r] ==23 & tem2$m2[r] ==23) {
>     tem2[[Ravg]][r] ==23} else if(tem2$m1[r] ==23 & tem2$m2[r] !=23){
>     tem2[[Ravg]][r] ==tem2$m2[r]} else if (tem2$m1[r] !=23 & tem2$m2[r]
> ==23) {
>     tem2[[Ravg]][r] ==tem2$m1[r]} else {
>     tem2[[Ravg]][r] == mean(tem2$m1[r] + tem2$m2[r])}
>                           }
>
> Thank you,
>
> Ding
>
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