Improvements to prime factorisation etc

Author: baddstats

DESCRIPTION

@@ -1,6 +1,6 @@
 Package: spatstat.utils
-Version: 3.1-2.001
-Date: 2025-01-13
+Version: 3.1-2.002
+Date: 2025-01-19
 Title: Utility Functions for 'spatstat'
 Authors@R: c(person("Adrian", "Baddeley", 
                     role = c("aut", "cre"),

NEWS

@@ -1,5 +1,5 @@
 
-        CHANGES IN spatstat.utils VERSION 3.1-2.001
+        CHANGES IN spatstat.utils VERSION 3.1-2.002
 
 OVERVIEW
 
@@ -11,6 +11,10 @@ NEW FUNCTIONS
     Recognise whether a given integer is a square number, a cube,
     or a power of another integer.
 
+SIGNIFICANT USER-VISIBLE CHANGES
+
+    o primefactors
+    Computation for large numbers improved.
 
         CHANGES IN spatstat.utils VERSION 3.1-2
 

R/primefactors.R

@@ -1,7 +1,7 @@
 #
 #  primefactors.R
 #
-#  $Revision: 1.14 $   $Date: 2025/01/13 09:01:24 $
+#  $Revision: 1.16 $   $Date: 2025/01/19 05:11:27 $
 #
 
 ## Table of prime numbers is now in sysdata object 'Spatstat.PrimesTable'
@@ -33,7 +33,8 @@ primefactors <- function(n, method=c("C", "interpreted")) {
   check.1.integer(n)
   if(n <= 0) return(integer(0))
   method <- match.arg(method)
-  if(method == "C" && n > .Machine$integer.max)
+  MaxInt <- .Machine$integer.max
+  if(method == "C" && n > MaxInt)
     method <- "interpreted"
   switch(method,
          interpreted = {
@@ -49,7 +50,8 @@ primefactors <- function(n, method=c("C", "interpreted")) {
                ## reduce problem size
                primedivisors <- candidateprimes[divides]
                result <- sort(c(result, primedivisors))
-               n <- as.integer(n/prod(primedivisors))
+               n <- n/prod(primedivisors)
+               if(n <= MaxInt) n <- as.integer(n)
                prmax <- floor(sqrt(n))
                candidateprimes <- primedivisors
              }
@@ -133,14 +135,16 @@ divisors <- local({
 is.square <- function(n) {
   check.1.integer(n)
   if(n < 0) return(FALSE)
-  tp <- table(primefactors(n))
-  all(tp %% 2 == 0)
+  v <- sqrt(n)
+  m <- c(floor(v), ceiling(v))
+  any(m^2 == n)
 }
 
 is.cube <- function(n) {
   check.1.integer(n)
-  tp <- table(primefactors(abs(n)))
-  all(tp %% 3 == 0)
+  v <- n^(1/3)
+  m <- c(floor(v), ceiling(v))
+  any(m^3 == n)
 }
 
 is.power <- function(n) {

inst/doc/packagesizes.txt

@@ -27,4 +27,4 @@ date version nhelpfiles nobjects ndatasets Rlines srclines
 "2024-06-17" "3.0-5" 41 189 0 3688 2031
 "2024-08-17" "3.1-0" 41 189 0 3613 2429
 "2024-11-02" "3.1-1" 41 189 0 3614 2429
-"2025-01-13" "3.1-2.001" 42 192 0 3646 2429
+"2025-01-19" "3.1-2.002" 42 192 0 3650 2429

inst/info/packagesizes.txt

@@ -27,4 +27,4 @@ date version nhelpfiles nobjects ndatasets Rlines srclines
 "2024-06-17" "3.0-5" 41 189 0 3688 2031
 "2024-08-17" "3.1-0" 41 189 0 3613 2429
 "2024-11-02" "3.1-1" 41 189 0 3614 2429
-"2025-01-13" "3.1-2.001" 42 192 0 3646 2429
+"2025-01-19" "3.1-2.002" 42 192 0 3650 2429