Handle diff() of long vector

Author: baddstats

DESCRIPTION

@@ -1,6 +1,6 @@
 Package: spatstat.utils
-Version: 3.2-0.002
-Date: 2025-11-19
+Version: 3.2-0.003
+Date: 2025-12-29
 Title: Utility Functions for 'spatstat'
 Authors@R: c(person("Adrian", "Baddeley", 
                     role = c("aut", "cre"),

NAMESPACE

@@ -48,6 +48,7 @@ export("choptext")
 export("choptextline")
 export("commasep")
 export("complaining")
+export("difflong")
 export("distpl")               
 export("distppl")
 export("distppll")

NEWS

@@ -1,5 +1,5 @@
 
-        CHANGES IN spatstat.utils VERSION 3.2-0.002
+        CHANGES IN spatstat.utils VERSION 3.2-0.003
 
 OVERVIEW
 

R/longvec.R

@@ -0,0 +1,38 @@
+#'
+#'  longvec.R
+#'
+#'  Utilities for long vectors
+#'
+#'  $Revision: 1.5 $ $Date: 2025/12/29 05:58:39 $
+
+difflong <- function(x, drop=TRUE) {
+  if(!is.null(dim(x))) stop("difflong is only implemented for vectors")
+  sm <- storage.mode(x)
+  switch(sm,
+         double = {
+           z <- .Call(C_Cdiffdouble,
+                      rx=as.double(x))
+         },
+         integer = {
+           z <- .Call(C_Cdiffint,
+                      rx=as.integer(x))
+         },
+         logical = {
+           z <- .Call(C_Cdiffint,
+                      rx=as.integer(x))
+         },
+         complex = {
+           Rez <- .Call(C_Cdiffdouble,
+                        rx=as.double(Re(x)))
+           Imz <- .Call(C_Cdiffdouble,
+                        rx=as.double(Im(x)))
+           z <- complex(real=Rez, imaginary=Imz)
+         },
+         stop(paste("difflong is not supported for vectors of type",
+                    sQuote(sm)),
+              call.=FALSE)
+         )
+  if(drop) z <- z[-1]
+  return(z)
+}
+

inst/doc/packagesizes.txt

@@ -31,4 +31,4 @@ date version nhelpfiles nobjects ndatasets Rlines srclines
 "2025-05-15" "3.1-4" 42 193 0 3689 2462
 "2025-07-17" "3.1-5" 42 194 0 3703 2462
 "2025-09-20" "3.2-0" 42 195 0 3716 2462
-"2025-11-19" "3.2-0.002" 42 195 0 3716 2462
+"2025-12-29" "3.2-0.003" 42 196 0 3754 2535

inst/info/packagesizes.txt

@@ -31,4 +31,4 @@ date version nhelpfiles nobjects ndatasets Rlines srclines
 "2025-05-15" "3.1-4" 42 193 0 3689 2462
 "2025-07-17" "3.1-5" 42 194 0 3703 2462
 "2025-09-20" "3.2-0" 42 195 0 3716 2462
-"2025-11-19" "3.2-0.002" 42 195 0 3716 2462
+"2025-12-29" "3.2-0.003" 42 196 0 3754 2535

man/spatstat.utils-internal.Rd

@@ -14,6 +14,7 @@
 \alias{choptext}
 \alias{choptextline}
 \alias{complaining}
+\alias{difflong}
 \alias{distpl}               
 \alias{distppl}
 \alias{distppll}
@@ -126,6 +127,7 @@ check.satisfies(cond, xname, should, context, fatal, warn)
 choptext(\dots, prefix, indent)
 choptextline(st, w, prefix, indent)
 complaining(whinge, fatal, value)
+difflong(x, drop)
 distpl(p, l)               
 distppl(p, l)
 distppll(p, l, mintype, method, listit)

src/init.c

@@ -38,9 +38,11 @@ static const R_CMethodDef CEntries[] = {
 };
 
 static const R_CallMethodDef CallEntries[] = {
-    {"circMseg", (DL_FUNC) &circMseg, 7},
-    {"circPseg", (DL_FUNC) &circPseg, 7},
-    {"circXseg", (DL_FUNC) &circXseg, 7},
+    {"Cdiffdouble", (DL_FUNC) &Cdiffdouble, 1},
+    {"Cdiffint",    (DL_FUNC) &Cdiffint,    1},
+    {"circMseg",    (DL_FUNC) &circMseg,    7},
+    {"circPseg",    (DL_FUNC) &circPseg,    7},
+    {"circXseg",    (DL_FUNC) &circXseg,    7},
     {NULL, NULL, 0}
 };
 

src/longvec.c

@@ -0,0 +1,69 @@
+#include <R.h>
+#include <Rinternals.h>
+
+/*
+
+  longvec.c
+
+  Operations for long vectors
+
+  Cdiffdouble     'diff'
+  Cdiffint
+  Cnzdiff         'nonzero diff'
+
+  $Revision: 1.4 $ $Date: 2025/12/29 05:36:18 $
+
+ */
+
+SEXP Cdiffdouble(SEXP rx) {
+  // diff for long vectors of doubles
+  R_xlen_t n = xlength(rx);
+  R_xlen_t i;
+  double *x = REAL(rx);
+  double xcur, xprev;
+  // compute successive differences, with leading 0
+  i = 1;
+  xprev = x[i];
+  for(i = 0; i < n; i++) {
+    xcur = x[i];
+    x[i] = xcur - xprev;
+    xprev = xcur;
+  }
+  return rx;
+}
+
+SEXP Cdiffint(SEXP rx) {
+  // diff for long vectors of integers
+  R_xlen_t n = xlength(rx);
+  R_xlen_t i;
+  // pointer to data
+  int *x = INTEGER(rx);
+  int xcur, xprev;
+  // compute successive differences, with leading 0
+  i = 1;
+  xprev = x[i];
+  for(i = 0; i < n; i++) {
+    xcur = x[i];
+    x[i] = xcur - xprev;
+    xprev = xcur;
+  }
+  return rx;
+}
+
+SEXP Cnzdiffint(SEXP rx) {
+  // test whether diff() is non-zero (with leading TRUE)
+  R_xlen_t n = xlength(rx);
+  R_xlen_t i;
+  // pointer to data
+  int *x = INTEGER(rx);
+  int xcur, xprev;
+  i = 1;
+  xprev = x[i];
+  for(i = 0; i < n; i++) {
+    xcur = x[i];
+    x[i] = (xcur == xprev)? 0:1;
+    xprev = xcur;
+  }
+  return rx;
+}
+

src/proto.h

@@ -35,6 +35,8 @@ void nnd2segs(double *, double *, int *, double *, double *, double *, double *,
              Functions invoked by .Call
 
 */
+SEXP Cdiffdouble(SEXP); SEXP Cdiffint(SEXP); SEXP Cdiffint(SEXP); 
+SEXP Cdiffdouble(SEXP); SEXP Cdiffdouble(SEXP);
 SEXP circXseg(SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP); 
 SEXP circMseg(SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP); 
 SEXP circPseg(SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP);