Reset path.from if nGroups changes in SplatParams

Fixes #36

R/SplatParams-methods.R

@@ -107,6 +107,11 @@ setMethod("setParam", "SplatParams",function(object, name, value) {
 
     if (name == "group.prob") {
         object <- setParamUnchecked(object, "nGroups", length(value))
+        path.from <- getParam(object, "path.from")
+        if (length(path.from) > 1 & length(path.from) != length(value)) {
+            warning("nGroups has changed, resetting path.from")
+            object <- setParam(object, "path.from", 0)
+        }
     }
 
     object <- callNextMethod()

tests/testthat/test-SplatParams.R

@@ -30,4 +30,7 @@ test_that("path.from checks work", {
     pp <- setParams(pp, group.prob = c(0.3, 0.3, 0.4))
     pp <- setParamUnchecked(pp, "path.from", c(2, 1, 1))
     expect_error(validObject(pp), "origin must be specified in path.from")
+    pp <- setParams(params, group.prob = c(0.5, 0.5), path.from = c(0, 1))
+    expect_warning(setParam(pp, "group.prob", 1),
+                   "nGroups has changed, resetting path.from")
 })