CODEWITHSUNDEEP
r
pricasari
pricasari

Reputation: 25

Copy observations based on the row number in R

My data frame (x) is:

c1 c2 

Aa 02 

Bb 03 

Cc 02

I'd like to create a column c3 copying the observation in c1 based on the row number in c2:

c1 c2 c3 

Aa 02 Bb 

Bb 03 Cc

Cc 02 Bb

I'm working with base R and I can't download packages.

Thank you!

Upvotes: 1

Views: 104

Answers (1)

Gregor Thomas
Gregor Thomas

Reputation: 146239

Using this data:

x = read.table(text = 'c1 c2 
Aa 02 
Bb 03 
Cc 02 ', header = T)

Here's a solution:

x$c3 = x$c1[as.numeric(as.character(x$c2))]
#   c1 c2 c3
# 1 Aa  2 Bb
# 2 Bb  3 Cc
# 3 Cc  2 Bb

as.numeric(as.character()) is a very safe way to convert something to numeric--it will work whether the source is factor or character (or already numeric). Though if you look at the class, class(x$c2) you can be more judicious about exactly what conversion is needed.

Upvotes: 3

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