CODEWITHSUNDEEP
r
WorldGov
WorldGov

Reputation: 157

Converting POSIXct or POSIXt to character results in a very large value in R

I'm having a bit of a weird issue.

x <- Sys.time()
x <- character(x)

This for some reason throws an error "Error: cannot allocate vector of size 11.9 Gb".

I faced a similar issue recently: I'm running code that accumulates information to a dataframe. Usually, this dataframe is about 6 MB. Today, this same dataframe from the same code is over 44 MB.

I'm new to parallel computing in R. Both these issues arose after I used doParallel and foreach so I'm guessing this has to do with one of these.

The parallelized segment looks like this:

  doParallel::registerDoParallel(cores = detectCores() - 1)

  <foreach code>

  stopImplicitCluster()

However, only the issue with the dataframe is related to this segment.

x <- Sys.time()
x <- character(x)

This still throws an error saying the character vector is too big even when I'm not running this part of the code (or even in a new R session).

Could my parallel code have changed something about how R behaves (permanently)?

Upvotes: 1

Views: 104

Answers (1)

akrun
akrun

Reputation: 887048

If the intention is to convert to character, it should be

as.character(x)

Or wrap with strftime which can also take format, tz arguments

strftime(Sys.time())

But, character(n) returns an blank vector of length 'n'. As Sys.time is stored as double, it will be coerced to a numeric value and that many times the "" is repeated i.e.

as.integer(Sys.time())
#[1] 1593382112

In my system, it returns something like

# ....
#99937] "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" #"" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" ""
#[99985] "" "" "" "" "" "" "" "" "" "" "" "" "" "" ""
# [ reached getOption("max.print") -- omitted 1593281954 entries ]


character(5)
#[1] "" "" "" "" ""

According to ?character, the usage is

character(length = 0)

where

length - A non-negative integer specifying the desired length. Double values will be coerced to integer: supplying an argument of length other than one is an error

Upvotes: 2

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