[R-pkg-devel] Slow down of as.POSIXct() when converting numeric data with origin specified

[Vincent van Hees]

Hello,
I am trying to make the as.POSIXct() calls in my R package (GGIR) backward
compatible with R 4.2.0 (from 2022) by always adding the origin =
"1970-01-01" argument to the as.POSIXct() calls. However, this causes a
substantial slow down when converting vectors of numeric time:

> time = Sys.time()> time = as.numeric(seq(time, time + 500000, by = 0.01))> print(system.time(A <- as.POSIXct(time)))   user  system elapsed
      0       0       0 > print(system.time(B <- as.POSIXct(time,
origin = "1970-01-01")))   user  system elapsed
  0.153   0.326   0.505


I am using R 4.2.2 on Ubuntu 22.04.
In real use cases this equates to hours rather than minutes of run time.

The only somewhat ugly solution I can think of is to rewrite the code as
if-else-statement where the if-branch is run with older R versions and uses
the origin argument, while the else-branch is run with later R versions and
does not use the origin argument.

Does anyone have a more elegant solution?

Thanks, Vincent

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