CODEWITHSUNDEEP
rif-statement
b222
b222

Reputation: 976

Multiple ifelse statement

I have the below df

      var1 var2  a1    a2
1    a    b      y     z
2    b    a      z     y
3    b    b      z     z

created from the following code

help <- data.frame(var1 = c("a", "b", "b"), var2 = c("b", "a", "b"), a1 = c(y, z, z), a2 = c(z, y, z))

my intention is to create an ifelse statement where I am able to (1) replace all a1 values to 'bp' when var1 equals 'a', and (2) replace all a2 values to 'bp' when var2 equals 'a'. I do not want to change the value if var1 or var2 is not 'a'.

Is the ifelse command not the best way to solve this problem? I started doing each one manually using help$a1[help$a1 == "a"] <- "bp" however, this will take a bit of time as I have multiple variables and a large dataset. Any assistance would be great.

Many thanks.

Upvotes: 0

Views: 314

Answers (1)

A. Webb
A. Webb

Reputation: 26446

You can use standard subsetting. Assuming per question edit that a1 and a2 are of class "character", then

df
#  var1 var2 a1 a2
#1    a    b  y  z
#2    b    a  z  y
#3    b    d  z  z

df[,3:4][df[,1:2]=="a"]<-"bp"

df
#  var1 var2 a1 b2
#1    a    b bp  z
#2    b    a  z bp
#3    b    d  z  z

You can also take advantage of your naming convention for the same

sel<-paste0("var",1:2)
mut<-paste0("a",1:2)
df[,mut][df[,sel]=="a"]<-"bp"

In either case the inner part, e.g. df[,sel]=="a" is returning a logical matrix the same shape as df[,sel] (and hence the same shape as df[,mut]), which is TRUE where and only where there was an "a". The outer part, e.g. df[,mut][...], uses that logical matrix to indicate the subset subject to the assignment.

Upvotes: 1

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