Question

Having a bit of a mental block. I am sure I found a function to print iteration numbers in a for loop that was not print and not cat, but gave the same output as cat below.

> for(i in 10^(1:5))  print(i)
[1] 10
[1] 100
[1] 1000
[1] 10000
[1] 1e+05
> for(i in 10^(1:5))  cat(i, "\n")
10 
100 
1000 
10000 
1e+05 

I cannot see any reference to it in the R help files for print and cat. Tried googling for it, but not getting anywhere.

Answer 1

It’s easy enough to define a wrapper function around cat:

catn <- function(x, append="\n"){cat(x); cat(append)}

Use it:

for(i in 10^(1:5))  catn(i)
10
100
1000
10000
1e+05

Or you can use message (which has the added benefit that in some code editors, e.g. Eclipse, the messages appear in a different colour):

for(i in 10^(1:5))  message(i)
10
100
1000
10000
1e+05