t.test(<Inf>,..) no longer errors unnecessarily

git-svn-id: https://svn.r-project.org/R/trunk@88283 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: maechler

doc/NEWS.Rd

@@ -118,6 +118,10 @@
       such as \code{if(TRUE)} now longer triggers a new browser level, fixing
       \PR{18885} (differently than the fix for \PR{15770}), with thanks to
       \I{Ivan Krylov}.
+
+      \item \code{t.test(c(1:3, Inf))} and similar no longer produce an error but
+      return a (still not so useful) \code{"htest"} result, fixing
+      \PR{18901}, thanks to \I{Jesse Alderliesten}.
     }
   }
 }

src/library/stats/R/t.test.R

@@ -1,7 +1,7 @@
 #  File src/library/stats/R/t.test.R
 #  Part of the R package, https://www.R-project.org
 #
-#  Copyright (C) 1995-2019 The R Core Team
+#  Copyright (C) 1995-2025 The R Core Team
 #
 #  This program is free software; you can redistribute it and/or modify
 #  it under the terms of the GNU General Public License as published by
@@ -60,7 +60,7 @@ function(x, y = NULL, alternative = c("two.sided", "less", "greater"),
         if(nx < 2) stop("not enough 'x' observations")
 	df <- nx-1
 	stderr <- sqrt(vx/nx)
-        if(stderr < 10 *.Machine$double.eps * abs(mx))
+        if(!is.na(stderr) && stderr < 10 *.Machine$double.eps * abs(mx))
             stop("data are essentially constant")
 	tstat <- (mx-mu)/stderr
 	method <- if(paired) "Paired t-test" else "One Sample t-test"
@@ -91,7 +91,7 @@ function(x, y = NULL, alternative = c("two.sided", "less", "greater"),
 	    stderr <- sqrt(stderrx^2 + stderry^2)
 	    df <- stderr^4/(stderrx^4/(nx-1) + stderry^4/(ny-1))
 	}
-        if(stderr < 10 *.Machine$double.eps * max(abs(mx), abs(my)))
+        if(!is.na(stderr) && stderr < 10 *.Machine$double.eps * max(abs(mx), abs(my)))
             stop("data are essentially constant")
         tstat <- (mx - my - mu)/stderr
     }

src/library/stats/man/t.test.Rd

@@ -1,6 +1,6 @@
 % File src/library/stats/man/t.test.Rd
 % Part of the R package, https://www.R-project.org
-% Copyright 1995-2023 R Core Team
+% Copyright 1995-2025 R Core Team
 % Distributed under GPL 2 or later
 
 \name{t.test}
@@ -69,6 +69,11 @@ t.test(x, \dots)
 
   If the input data are effectively constant (compared to the larger of the
   two means) an error is generated.
+
+  If the data contain infinite values, \code{t.test()} no longer errors and
+  returns a still not very useful result.  Note that
+  \code{\link{wilcox.test()}} is \emph{robust} against outliers and hence
+  deals more usefully with such \code{Inf} values in \code{x} or \code{y}.
 }
 \value{
   A list with class \code{"htest"} containing the following components:

tests/reg-tests-1e.R

@@ -1981,6 +1981,21 @@ stopifnot(exprs = {
 ## subsetting only kept "table" class in R <= 4.5.x
 
 
+## t.test(<Inf>...) -- PR#18901
+x <- c(1:6,Inf); y <- c(1:20, Inf); yN <- c(-Inf, 1:20)
+(tt1 <- t.test(x))
+tt2. <- t.test(x, y)
+(tt2N <- t.test(x, yN))
+stopifnot(exprs = {
+    inherits(tt1,  "htest"); is.na(c(tt1 $p.value, tt1 $conf.int))
+    inherits(tt2., "htest"); is.na(c(tt2.$p.value, tt2.$conf.int))
+    inherits(tt2N, "htest"); is.na(c(tt2N$p.value, tt2N$conf.int))
+    tt1$estimate == Inf
+    tt2N$estimate == c(Inf, -Inf)
+})
+## The t.test() calls errored all in R <= 4.5.1
+
+
 
 ## keep at end
 rbind(last =  proc.time() - .pt,