How to add leading zeros in R

Question

Consider the following code:

a <- seq(1,101,25)
b <- paste("sequence", 1:length(a), sep = "_")

produces the following output:

"sequence_1"  "sequence_26"  "sequence_51"  "sequence_76"  "sequence_101"

I want to have the same width of all values i.e. I want to fill the values with zeros as follows:

I'd like to have the same width of all values which means for me to fill the values with zeros like this:

"sequence_001"  "sequence_026"  "sequence_051"  "sequence_076"  "sequence_101"

How do I do that?

Answer 1

There are several solutions to this.

One of them is to use sprintf. This uses C style formatting codes embedded in a character string to indicate the format of any other arguments passed to it.

 For example, the formatting code %3dmeans format a number as an integer of width 3:

a <- seq(1,101,25)
sprintf("sequence_%03d", a)
[1] "sequence_001" "sequence_026" "sequence_051" "sequence_076" "sequence_101"

Another option is formatC and paste:

paste("sequence", formatC(a, width=3, flag="0"), sep="_")
[1] "sequence_001" "sequence_026" "sequence_051" "sequence_076" "sequence_101"