model.frame() gives more informative error when not finding a variable

git-svn-id: https://svn.r-project.org/R/trunk@88018 00db46b3-68df-0310-9c12-caf00c1e9a41

Author: maechler

doc/NEWS.Rd

@@ -240,6 +240,10 @@
       \item \code{isSymmetric(<matrix>)} gains a new option \code{trans = "C"};
       when set to non-default, it tests for \dQuote{simple} symmetry of
       complex matrices.
+
+      \item \code{model.frame()} produces more informative error messages
+      in some cases when variables in the formula are not found, thanks to
+      \I{Ben Bolker}'s \PR{18860}.
     }
   }
 

src/library/stats/src/model.c

@@ -136,7 +136,6 @@ SEXP modelframe(SEXP call, SEXP op, SEXP args, SEXP rho)
     nc = length(data);
     nr = 0;			/* -Wall */
     if (nc > 0) {
-	nr = nrows(VECTOR_ELT(data, 0));
 	for (i = 0; i < nc; i++) {
 	    ans = VECTOR_ELT(data, i);
 	    switch(TYPEOF(ans)) {
@@ -152,6 +151,7 @@ SEXP modelframe(SEXP call, SEXP op, SEXP args, SEXP rho)
 		      R_typeToChar(ans),
 		      translateChar(STRING_ELT(names, i)));
 	    }
+	    nr = nrows(VECTOR_ELT(data, 0));
 	    if (nrows(ans) != nr)
 		error(_("variable lengths differ (found for '%s')"),
 		      translateChar(STRING_ELT(names, i)));

tests/reg-tests-1e.R

@@ -1879,6 +1879,37 @@ stopifnot(exprs = {
 ## In max(lens) : no non-missing arguments to max; returning -Inf
 
 
+## better error messages when not finding variables in  model.frame() -- PR#18860
+dd  <- mtcars ; m <- model.matrix(mpg ~ wt, data = dd) # fine
+dd2 <- dd[-match("mpg", names(dd))]
+if(exists("mpg")) rm(mpg)
+getErrMsg <- function(expr) conditionMessage(assertErrV( expr )[[1L]])
+eee <- c(
+    getErrMsg(m <- model.matrix(mpg ~ wt, data = dd2))
+    ,
+    getErrMsg(local({
+        mpg <- USJudgeRatings
+        model.matrix(mpg ~ wt, data = dd2) # still useful
+    }))
+    ,
+    getErrMsg(local({
+        model.matrix(count ~ wt, data = dd)
+    })) ## OK (i.e. useful error message, "object 'count' not found")
+    ,
+    getErrMsg(local({
+        count <- function(x, ..., wt = NULL) { UseMethod("count") }
+        model.matrix(count ~ wt, data = dd)
+    }))
+)
+if(englishMsgs)
+    stopifnot(identical(
+        eee,
+        c("object 'mpg' not found",
+          "invalid type (list) for variable 'mpg'",
+          "object 'count' not found",
+          "invalid type (closure) for variable 'count'")))
+## the last one differed 
+
 
 ## keep at end
 rbind(last =  proc.time() - .pt,