gw*degree(0, fixed = TRUE) no longer produces NaNs and does not cause errors when the network has no *isolates. Thanks to Kevin Reuning (@reuning) for the report.

fixes #602

Author: krivit

R/InitErgmTerm.R

@@ -2626,11 +2626,13 @@ InitErgmTerm.gwb1dsp<-function(nw, arglist, cache.sp=TRUE, gw.cutoff=30, ...) {
 #' @templateVar name gwb2degree
 #' @title Geometrically weighted degree distribution for the second mode in a bipartite network
 #' @description This term adds one network statistic to the model equal to the weighted
-#'   degree distribution with decay controlled by the which should be non-negative,
-#'   for nodes in the
-#'   second mode of a bipartite network. The second mode of a bipartite network
+#'   degree distribution with decay controlled by the `decay` parameter, which should be non-negative,
+#'   for nodes in the second mode of a bipartite network. The second mode of a bipartite network
 #'   object is sometimes known as the "event" mode.
-#'   
+#'
+#'   This term can only be used with undirected bipartite
+#'   networks.
+#'
 #' @usage
 #' # binary: gwb2degree(decay, fixed=FALSE, attr=NULL, cutoff=30, levels=NULL)
 #'
@@ -2738,7 +2740,7 @@ InitErgmTerm.gwidegree<-function(nw, arglist, gw.cutoff=30, ..., version=package
 #' @title Geometrically weighted out-degree distribution
 #' @description This term adds one network statistic to the model
 #'   equal to the weighted out-degree distribution with decay parameter
-#'   `decay` parameter, which should be non-negative. This
+#'   `decay` parameter, which should be positive. This
 #'   term can only be used with directed networks.
 #'   
 #' @usage

man/gwb2degree-ergmTerm-584e787c.Rd

@@ -1873,6 +1873,9 @@ S_CHANGESTAT_FN(s_edges) {
 /*****************
  changestat: d_gwdegree
 *****************/
+
+#define GWD0(d0) ((decay) ? exp(loneexpd*(d0)) : (d0)==0)
+
 C_CHANGESTAT_FN(c_gwdegree) { 
   int  echange=0;
   double decay, loneexpd, change;
@@ -1885,10 +1888,10 @@ C_CHANGESTAT_FN(c_gwdegree) {
 
   /* *** don't forget tail -> head */    
   change = 0.0;
-    echange = edgestate ? -1:+1;
-    taild = od[tail] + id[tail] + (echange - 1)/2;
-    headd = od[head] + id[head] + (echange - 1)/2;
-    change += echange*(exp(loneexpd*taild)+exp(loneexpd*headd));
+  echange = edgestate ? -1:+1;
+  taild = od[tail] + id[tail] - edgestate;
+  headd = od[head] + id[head] - edgestate;
+  change += echange*(GWD0(taild) + GWD0(headd));
 
   CHANGE_STAT[0] = change;
 
@@ -1914,13 +1917,13 @@ C_CHANGESTAT_FN(c_gwdegree_by_attr) {
 
   /* *** don't forget tail -> head */    
     echange = edgestate ? -1:+1;
-    taild = od[tail] + id[tail] + (echange - 1)/2;
+    taild = od[tail] + id[tail] - edgestate;
     tailattr = INPUT_PARAM[tail]; 
-    CHANGE_STAT[tailattr-1] += echange*exp(loneexpd*taild);
+    CHANGE_STAT[tailattr-1] += echange*GWD0(taild);
 
-    headd = od[head] + id[head] + (echange - 1)/2;
+    headd = od[head] + id[head] - edgestate;
     headattr = INPUT_PARAM[head]; 
-    CHANGE_STAT[headattr-1] += echange*exp(loneexpd*headd);
+    CHANGE_STAT[headattr-1] += echange*GWD0(headd);
 
 }
 
@@ -1937,7 +1940,7 @@ C_CHANGESTAT_FN(c_gwidegree) {
 
   /* *** don't forget tail -> head */    
     headd = IN_DEG[head] - edgestate;
-    change += (edgestate? -1.0 : 1.0) * exp(loneexpd*headd);
+    change += (edgestate? -1.0 : 1.0) * GWD0(headd);
   CHANGE_STAT[0]=change; 
 }
 
@@ -1959,9 +1962,9 @@ C_CHANGESTAT_FN(c_gwidegree_by_attr) {
 
   /* *** don't forget tail -> head */    
     echange = edgestate ? -1 : 1;
-    headd = IN_DEG[head] + (echange - 1)/2;
+    headd = IN_DEG[head] - edgestate;
     headattr = INPUT_PARAM[head - BIPARTITE]; /* BIPARTITE to make the b2 version a special case. */
-    CHANGE_STAT[headattr-1] += echange*exp(loneexpd*headd);
+    CHANGE_STAT[headattr-1] += echange*GWD0(headd);
 }
 
 /*****************
@@ -1977,7 +1980,7 @@ C_CHANGESTAT_FN(c_gwodegree) {
 
   /* *** don't forget tail -> head */    
     taild = OUT_DEG[tail] - edgestate;
-    change += (edgestate? -1 : 1) * exp(loneexpd*taild);
+    change += (edgestate? -1 : 1) * GWD0(taild);
   CHANGE_STAT[0] = change;
 }
 
@@ -1999,9 +2002,9 @@ C_CHANGESTAT_FN(c_gwodegree_by_attr) {
 
   /* *** don't forget tail -> head */    
     echange = edgestate ? -1 : 1;
-    taild = OUT_DEG[tail] + (echange - 1)/2;
+    taild = OUT_DEG[tail] - edgestate;
     tailattr = INPUT_PARAM[tail]; 
-    CHANGE_STAT[tailattr-1] += echange*exp(loneexpd*taild);
+    CHANGE_STAT[tailattr-1] += echange*GWD0(taild);
 }
 
 /********************  changestats:  H    ***********/

man/gwodegree-ergmTerm-276e606c.Rd

@@ -88,6 +88,10 @@ test_that("gwodegree, directed", {
   expect_summary(head(s.d), e.d, setNames(c(0,0,1,5,7,5), paste0("gwodegree#",1:6)), c(gwodeg.fixed.0.4=-1.990492))
   expect_summary(s.df, e.df, 24.23040, 43.61801)
   expect_summary(s.dfa, e.dfa, c(7.735906, 4.419631, 7.736070), -c(4.1860720, 5.9706455, 0.4921623))
+
+  # Also, check that gwodegree(0) works correctly, including when there are none.
+  expect_equal(summary(samplike~gwodegree(0, fixed = TRUE)), network.size(samplike), ignore_attr = TRUE)
+  expect_equal(coef(ergm(samplike~edges + gwodegree(0, fixed = TRUE), estimate="MPLE"))[[2]], +Inf)
 })
 
 test_that("idegree, directed", {

man/spcachenet-ergmAuxiliary-f1950bb3.Rd

@@ -126,6 +126,9 @@ test_that("gwdegree, undirected", {
   expect_summary(s.dfa, e.dfa,
     c(53.58148, 25.53534, 30.83418, 17.79934, 19.31326, 10.80933),
     -c(23.94060, 23.30646, 23.51430, 23.31140, 25.11103, 26.88088))
+
+  # Also, check that gwdegree(0) is evaluates correctly.
+  expect_equal(summary(fmh ~ gwdegree(0, fixed=TRUE)), network.size(fmh) - summary(fmh ~ degree(0)), ignore_attr = TRUE)
 })
 
 test_that("kstar, undirected", {