rdecimaldigitisolationtruncated

How do you isolate the digits following a decimal in R?

For example: I have the number 123.456 and want to return 456.

The function trunc() basically isolates (truncates) the numbers before the decimal.

Is there a function to isolate just the digits after the decimal?

Two follow-up questions:

  1. Is there a way to do this without writing out the regex?

  2. What if I want to maintain the sign? For example, if I wanted to (reverse) truncate -123.456 to -456.

Solution

  • Using the modulo operator (%%) with 1 as the devisor works I guess. It does successfully isolate the numbers following the decimal, but leaves the decimal:

    123.456 %% 1
[1] 0.456

    However it only works for positive numbers in that the sign is not preserved nor are the proper numbers reported (b/c of modulo operator's functionality):

    -123.456 %% 1
[1] 0.544  #not what is wanted

    Including abs() fixes that issue, but doesn't help report sign. Sign could be included by adding:

    sign(x) * (abs(x) %% 1)

    If we really wanted to report just the digits after the decimal (i.e., excluding the 0 and the decimal), we could do the following (presented in 2 steps for clarity):

    x <- -123.456
y <- sign(x) * (abs(x) %% 1)
as.numeric(gsub("0.","",y))
[1] -456  #as desired from part 2 in the OP