Dear all,
I just have identified the following issue which I believe could be a bug in R:
Let me illustrate:
First, enable the display of fractional seconds and check that it works:
> options(digits.secs = 6, digits = 6)
> as.character(as.POSIXct("2018-08-31 14:15:16.123456"))
[1] "2018-08-31 14:15:16.123456"
Now create a sequence of POSIXct with stepwidth 0.1sec:
> test <- as.POSIXct("2018-08-31 14:15:16.000000")
> test_seq <- seq(test, test + 1, by = 1/10)
Calling format with the millisecond conversion specification gives the intended
result (even though there is a small representation error):
> format(test_seq, "%F %T.%OS")
[1] "2018-08-31 14:15:16.16.000000" "2018-08-31 14:15:16.16.099999"
"2018-08-31 14:15:16.16.200000" "2018-08-31 14:15:16.16.299999"
[5] "2018-08-31 14:15:16.16.400000" "2018-08-31 14:15:16.16.500000"
"2018-08-31 14:15:16.16.599999" "2018-08-31 14:15:16.16.700000"
[9] "2018-08-31 14:15:16.16.799999" "2018-08-31 14:15:16.16.900000"
"2018-08-31 14:15:17.17.000000"
However, if I use as.character, the milliseconds seemingly just get cut-off
after one digit, resulting in incorrect representations:
> as.character(test_seq)
[1] "2018-08-31 14:15:16.0" "2018-08-31 14:15:16.0" "2018-08-31 14:15:16.2"
"2018-08-31 14:15:16.2" "2018-08-31 14:15:16.4" "2018-08-31 14:15:16.5"
[7] "2018-08-31 14:15:16.5" "2018-08-31 14:15:16.7" "2018-08-31 14:15:16.7"
"2018-08-31 14:15:16.9" "2018-08-31 14:15:17.0"
It seems to me, that R correctly decides that there is only one significant
digit after the decimal point, but then incorrectly (due to representation
error) just cuts off after the first digit.
BR,
Andreas
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