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Duncan Murdoch
On 05/02/2021 4:01 p.m., Christopher Carbone wrote:
Greetings,
I found a bug in the cut.Date function of base R. My session info is
at the bottom.
The bug is in the "months" section of the code. Consider the following:
# Create vector with 365 days of year and cut into 12 months
dates <- seq(as.Date("2021-1-1"),as.Date("2021-12-31"),by="day")
months <- cut(dates,"months",labels=1:12)
table(months)
# months
# 1 2 3 4 5 6 7 8 9 10 11 12
# 31 28 31 30 31 30 31 31 30 31 30 31
# cut.Date works perfectly
# Extend dates vector by adding following January and cut into 13 months
dates <- seq(as.Date("2021-1-1"),as.Date("2022-1-31"),by="day")
months <- cut(dates,"months",labels=1:13)
# Error in cut.default(unclass(x), unclass(breaks), labels = labels,
right = right, :
# lengths of 'breaks' and 'labels' differ
months <- cut(dates,"months",labels=1:14)
table(months)
# months
# 1 2 3 4 5 6 7 8 9 10 11 12 13 14
# 31 28 31 30 31 30 31 31 30 31 30 31 31 0
# Bug: cut.Date adds a superfluous bin
# This is because February has less than 31 days
# Thus, the code adjusts the end into March instead of February
Inspecting the source code, I see the problem resides in lines 31
through 41, the section dealing with breaks="months":
if (valid == 3L) {
start$mday <- 1L
start$isdst <- -1L
end <- as.POSIXlt(max(x, na.rm = TRUE))
step <- if (length(by2) == 2L)
as.integer(by2[1L])
else 1L
38 end <- as.POSIXlt(end + (31 * step * 86400))
end$mday <- 1L
end$isdst <- -1L
breaks <- as.Date(seq(start, end, breaks))
When the end is adjusted in line 38, there are instances where an
unnecessary extra bin is created.
This is accounted for in the breaks="quarters" case by testing at the
end and removing the final break if necessary.
The same method employed here fixes the bug:
if (valid == 3L) {
start$mday <- 1L
start$isdst <- -1L
maxx <- max(x, na.rm = TRUE) # Added line
end <- as.POSIXlt(maxx) # Modified line
step <- if (length(by2) == 2L)
as.integer(by2[1L])
else 1L
end <- as.POSIXlt(end + (31 * step * 86400))
end$mday <- 1L
end$isdst <- -1L
breaks <- as.Date(seq(start, end, breaks))
lb <- length(breaks) # Added line
if (maxx < breaks[lb - 1]) # Added line
breaks <- breaks[-lb] # Added line
I modified cut.Date with the above code changes and stored it in a
function called cut_Date():
dates <- seq(as.Date("2021-1-1"),as.Date("2022-1-31"),by="day")
months <- cut_Date(dates,"months",labels=1:13)
table(months)
# months
# 1 2 3 4 5 6 7 8 9 10 11 12 13
# 31 28 31 30 31 30 31 31 30 31 30 31 31
Thanks for your time and consideration!
sessionInfo()
R version 4.0.3 (2020-10-10)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 19041)
Matrix products: default
locale:
[1] LC_COLLATE=English_United States.1252 LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C
[5] LC_TIME=English_United States.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] compiler_4.0.3 tools_4.0.3 tinytex_0.28 xfun_0.19
Many Blessings,
Christopher Carbone
"Follow your bliss and doors will open where you didn't know they were
going to be..."
-Joseph Campbell
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