R programming question: insert alternately

Hi Guys,

I have a quick question:

I have list of characters in two different objects

object1

 "1.TY"   "2.TY"   "4.TY"   "5.TY"

object2

"1.MN"   "2.MN"   "4.MN"   "5.MN"

I want to merge them alternating one after other, as shown below.

Result

"1.TY"  "1.MN"  "2.TY" "2.MN"  "4.TY" "4.MN"  "5.TY"  "5.MN"

Thank you for your help.

• 3,614 views • link

updated 4.1 years ago by Ram

• written 11.3 years ago by MAPK

4 answers

For anyone else interested in the different performance of these solutions, I did a crude comparison.

The TLDR would be: the "grow a for loop" approach works for short vectors, but scales terribly. The rbind method, as unintuitive as it might be, is the fastest of the lot

• 0 views • link

updated 4.1 years ago by Ram

• written 11.3 years ago by David W

a <- c("1.TY","2.TY","4.TY","5.TY")
b <- c("1.MN","2.MN","4.MN","5.MN")
results <- c()
for (i in 1:4){
  results <- c(results, a[i], b[i])
}
> results
[1] "1.TY" "1.MN" "2.TY" "2.MN" "4.TY" "4.MN" "5.TY" "5.MN"

Enjoy :)

• 1 views • link

updated 4.1 years ago by Ram

• written 11.3 years ago by TriS

This should get the job done, and for shorter vectors won't take too long. But be aware, starting an empty vector and growing it like this, though sensible in many languages, is usually very slow in r. I've not tested it, but as.character(rbind(a,b)) should work, and starting a vector of the final size and filling it by index (using seq() ) would likely be faster.

• 1 views • link

written 11.3 years ago by David W

Thank you, got what I need.

• 1 views • link

written 11.3 years ago by MAPK

This solution might be preferable in R as it should be orders of magnitude faster than a for-loop (although in practice it might not matter):

a <- c("1.TY","2.TY","4.TY","5.TY", "0.TY")
b <- c("1.MN","2.MN","4.MN","5.MN", "0.MN")
ord<- order(c(1:length(a), 1:length(b)))
results<- c(a, b)[ord]
> results
 [1] "1.TY" "1.MN" "2.TY" "2.MN" "4.TY" "4.MN" "5.TY" "5.MN" "0.TY" "0.MN"

• 1 views • link

updated 4.1 years ago by Ram

• written 11.3 years ago by dariober

Use the interleave-function from ggplot2-package

• 0 views • link

written 11.3 years ago by Irsan