>>>>> "EL" == Eberhard Lisse <nos...@lisse.na>
>>>>> on Thu, 24 Apr 2014 01:21:37 +0100 writes:
EL> In MySQL
EL> SELECT INET_ATON('127.0.0.1')
EL> returns the integer 2130706433
EL> Is there a function in R to reverse that, ie so that something like
EL> ip <- inet_ntoa(2130706433)
EL> would put '127.0.0.1' into ip?
almost:
install.packages("sfsmisc")
require("sfsmisc")
# NTOA :
> digitsBase(2130706433, base = 256)
Class 'basedInt'(base = 256) [1:1]
[,1]
[1,] 127
[2,] 0
[3,] 0
[4,] 1
# ATON :
> as.intBase(digitsBase(2130706433, base = 256), base = 256)
1
2130706433
>
So, an easy solution seems
> ip.ntoa <- function(n) paste(sfsmisc::digitsBase(n, base = 256), collapse=".")
> ip.ntoa(2130706433)
[1] "127.0.0.1"
>
but that does not vectorize (work for length(n) > 1 )
correctly.
The correct solution then is
ip.ntoa <- function(n)
apply(sfsmisc::digitsBase(n, base = 256), 2, paste, collapse=".")
and that does work nicely:
> ip.ntoa(1000000000+ (0:10))
[1] "59.154.202.0" "59.154.202.1" "59.154.202.2" "59.154.202.3"
"59.154.202.4"
[6] "59.154.202.5" "59.154.202.6" "59.154.202.7" "59.154.202.8"
"59.154.202.9"
[11] "59.154.202.10"
right ?
--
Martin Maechler, ETH Zurich
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