Fix week() calculation to start week 1 at days 1–7

NAMESPACE

@@ -57,6 +57,9 @@ export(frollsum)
 export(frollmax)
 export(frollmin)
 export(frollprod)
+export(frollmedian)
+export(frollvar)
+export(frollsd)
 export(frollapply)
 export(frolladapt)
 export(nafill)

NEWS.md

@@ -246,7 +246,52 @@
     #9: 2025-09-22     9         8           9.0
     ```
 
-19. New rolling functions, `frollmin` and `frollprod`, have been implemented, towards [#2778](https://github.com/Rdatatable/data.table/issues/2778). Thanks to @jangorecki for implementation.
+19. Other new rolling functions: `frollmin`, `frollprod`, `frollmedian`, `frollvar` and `frollsd`, have been implemented, resolving long standing issue [#2778](https://github.com/Rdatatable/data.table/issues/2778). Thanks to @jangorecki for implementation. Implementation of rolling median is based on a novel algorithm "sort-median" described by [@suomela](https://github.com/suomela) in his 2014 paper [Median Filtering is Equivalent to Sorting](https://arxiv.org/abs/1406.1717). "sort-median" scales very well, not only for size of input vector but also for size of rolling window.
+    ```r
+    rollmedian = function(x, n) {
+      ans = rep(NA_real_, nx<-length(x))
+      if (n<=nx) for (i in n:nx) ans[i] = median(x[(i-n+1L):(i)])
+      ans
+    }
+    library(data.table)
+    setDTthreads(8)
+    set.seed(108)
+    x = rnorm(1e5)
+
+    n = 100
+    system.time(rollmedian(x, n))
+    #   user  system elapsed
+    #  2.049   0.001   2.051
+    system.time(frollapply(x, n, median, simplify=unlist))
+    #   user  system elapsed
+    #  3.071   0.223   0.436
+    system.time(frollmedian(x, n))
+    #   user  system elapsed
+    #  0.013   0.000   0.004
+
+    n = 1000
+    system.time(rollmedian(x, n))
+    #   user  system elapsed
+    #  3.496   0.009   3.507
+    system.time(frollapply(x, n, median, simplify=unlist))
+    #   user  system elapsed
+    #  4.552   0.307   0.632
+    system.time(frollmedian(x, n))
+    #   user  system elapsed
+    #  0.015   0.000   0.004
+
+    n = 10000
+    system.time(rollmedian(x, n))
+    #   user  system elapsed
+    # 16.350   0.025  16.382
+    system.time(frollapply(x, n, median, simplify=unlist))
+    #   user  system elapsed
+    # 14.865   0.722   2.267
+    system.time(frollmedian(x, n))
+    #   user  system elapsed
+    #  0.028   0.000   0.005
+    ```
+    20. `fread()` now supports the `comment.char` argument to skip trailing comments or comment-only lines, consistent with `read.table()`, [#856](https://github.com/Rdatatable/data.table/issues/856). The default remains `comment.char = ""` (no comment parsing) for backward compatibility and performance, in contrast to `read.table(comment.char = "#")`. Thanks to @arunsrinivasan and many others for the suggestion and @ben-schwen for the implementation.
 
 ### BUG FIXES
 
@@ -288,6 +333,8 @@
 
 19. Ellipsis elements like `..1` are correctly excluded when searching for variables in "up-a-level" syntax inside `[`, [#5460](https://github.com/Rdatatable/data.table/issues/5460). Thanks @ggrothendieck for the report and @MichaelChirico for the fix.
 
+20. BREAKING CHANGE: `week()` now calculates the week of the year sequentially (days 1-7 are week 1), fixing a bug where the first week could have 6 days. A one-time warning is now issued if this change affects the output for a given input, which can be disabled via `options(datatable.warn.week.change = FALSE)`. [#2611](https://github.com/Rdatatable/data.table/issues/2611). Thanks to @MichaelChirico for the report and @venom1204 for the fix.
+
 ### NOTES
 
 1. The following in-progress deprecations have proceeded:

R/fread.R

@@ -2,7 +2,7 @@ fread = function(
 input="", file=NULL, text=NULL, cmd=NULL, sep="auto", sep2="auto", dec="auto", quote="\"", nrows=Inf, header="auto",
 na.strings=getOption("datatable.na.strings","NA"), stringsAsFactors=FALSE, verbose=getOption("datatable.verbose",FALSE),
 skip="__auto__", select=NULL, drop=NULL, colClasses=NULL, integer64=getOption("datatable.integer64","integer64"),
-col.names, check.names=FALSE, encoding="unknown", strip.white=TRUE, fill=FALSE, blank.lines.skip=FALSE, key=NULL, index=NULL,
+col.names, check.names=FALSE, encoding="unknown", strip.white=TRUE, fill=FALSE, blank.lines.skip=FALSE, comment.char="", key=NULL, index=NULL,
 showProgress=getOption("datatable.showProgress",interactive()), data.table=getOption("datatable.fread.datatable",TRUE),
 nThread=getDTthreads(verbose), logical01=getOption("datatable.logical01",FALSE),
 logicalYN=getOption("datatable.logicalYN", FALSE),
@@ -30,6 +30,9 @@ yaml=FALSE, tmpdir=tempdir(), tz="UTC")
     isTRUEorFALSE(stringsAsFactors) || (is.double(stringsAsFactors) && length(stringsAsFactors)==1L && 0.0<=stringsAsFactors && stringsAsFactors<=1.0),
     is.numeric(nrows), length(nrows)==1L
   )
+  if (!is.character(comment.char) || length(comment.char) != 1L || is.na(comment.char) || nchar(comment.char) > 1L) {
+    stopf("comment.char= must be a single non-NA character.")
+  }
   fill = if(identical(fill, Inf)) .Machine$integer.max else as.integer(fill)
   nrows=as.double(nrows) #4686
   if (is.na(nrows) || nrows<0L) nrows=Inf   # accept -1 to mean Inf, as read.table does
@@ -289,7 +292,7 @@ yaml=FALSE, tmpdir=tempdir(), tz="UTC")
     if (identical(tt,"") || is_utc(tt)) # empty TZ env variable ("") means UTC in C library, unlike R; _unset_ TZ means local
       tz="UTC"
   }
-  ans = .Call(CfreadR,input,identical(input,file),sep,dec,quote,header,nrows,skip,na.strings,strip.white,blank.lines.skip,
+  ans = .Call(CfreadR,input,identical(input,file),sep,dec,quote,header,nrows,skip,na.strings,strip.white,blank.lines.skip,comment.char,
               fill,showProgress,nThread,verbose,warnings2errors,logical01,logicalYN,select,drop,colClasses,integer64,encoding,keepLeadingZeros,tz=="UTC")
   if (!length(ans)) return(null.data.table())  # test 1743.308 drops all columns
   nr = length(ans[[1L]])

R/froll.R

@@ -213,3 +213,12 @@ frollmin = function(x, n, fill=NA, algo=c("fast","exact"), align=c("right","left
 frollprod = function(x, n, fill=NA, algo=c("fast","exact"), align=c("right","left","center"), na.rm=FALSE, has.nf=NA, adaptive=FALSE, partial=FALSE, give.names=FALSE, hasNA) {
   froll(fun="prod", x=x, n=n, fill=fill, algo=algo, align=align, na.rm=na.rm, has.nf=has.nf, adaptive=adaptive, partial=partial, hasNA=hasNA, give.names=give.names)
 }
+frollmedian = function(x, n, fill=NA, algo=c("fast","exact"), align=c("right","left","center"), na.rm=FALSE, has.nf=NA, adaptive=FALSE, partial=FALSE, give.names=FALSE, hasNA) {
+  froll(fun="median", x=x, n=n, fill=fill, algo=algo, align=align, na.rm=na.rm, has.nf=has.nf, adaptive=adaptive, partial=partial, hasNA=hasNA, give.names=give.names)
+}
+frollvar = function(x, n, fill=NA, algo=c("fast","exact"), align=c("right","left","center"), na.rm=FALSE, has.nf=NA, adaptive=FALSE, partial=FALSE, give.names=FALSE, hasNA) {
+  froll(fun="var", x=x, n=n, fill=fill, algo=algo, align=align, na.rm=na.rm, has.nf=has.nf, adaptive=adaptive, partial=partial, hasNA=hasNA, give.names=give.names)
+}
+frollsd = function(x, n, fill=NA, algo=c("fast","exact"), align=c("right","left","center"), na.rm=FALSE, has.nf=NA, adaptive=FALSE, partial=FALSE, give.names=FALSE, hasNA) {
+  froll(fun="sd", x=x, n=n, fill=fill, algo=algo, align=align, na.rm=na.rm, has.nf=has.nf, adaptive=adaptive, partial=partial, hasNA=hasNA, give.names=give.names)
+}