--- a/doc/interpreter/tips.txi	Fri Aug 29 13:27:36 2014 -0700
+++ b/doc/interpreter/tips.txi	Fri Aug 29 16:30:11 2014 -0700
@@ -500,7 +500,8 @@
 @@deftypefn  @{Function File@} @{@@var@{c@} =@} nchoosek (@@var@{n@}, @@var@{k@})
 @@deftypefnx @{Function File@} @{@@var@{c@} =@} nchoosek (@@var@{set@}, @@var@{k@})
 
-Compute the binomial coefficient or all combinations of a set of items.
+Compute the binomial coefficient of @@var@{n@} or list all possible
+combinations of a @@var@{set@} of items.
 
 If @@var@{n@} is a scalar then calculate the binomial coefficient
 of @@var@{n@} and @@var@{k@} which is defined as
@@ -554,10 +555,10 @@
 @@end group
 @@end example
 
-@@code@{nchoosek@} works only for non-negative, integer arguments.  Use
-@@code@{bincoeff@} for non-integer and negative scalar arguments, or for
-computing many binomial coefficients at once with vector inputs
-for @@var@{n@} or @@var@{k@}.
+Programming Note: When calculating the binomial coefficient @@code@{nchoosek@}
+works only for non-negative, integer arguments.  Use @@code@{bincoeff@} for
+non-integer and negative scalar arguments, or for computing many binomial
+coefficients at once with vector inputs for @@var@{n@} or @@var@{k@}.
 
 @@seealso@{bincoeff, perms@}
 @@end deftypefn
@@ -566,7 +567,7 @@
 @noindent
 which demonstrates most of the concepts discussed above.
 @iftex
-This documentation string renders as
+This documentation string renders in Info format as
 @c Note: use the actual output of info below, rather than try and 
 @c reproduce it here to prevent it looking different from how it would
 @c appear with info.
@@ -574,8 +575,8 @@
 @example
  -- Function File: C = nchoosek (N, K)
  -- Function File: C = nchoosek (SET, K)
-     Compute the binomial coefficient or all combinations of a set of
-     items.
+     Compute the binomial coefficient of N or list all possible
+     combinations of a SET of items.
 
      If N is a scalar then calculate the binomial coefficient of N and
      K which is defined as
@@ -608,32 +609,31 @@
                  1   3
                  2   3
 
+     Programming Note: When calculating the binomial coefficient
      `nchoosek' works only for non-negative, integer arguments.  Use
      `bincoeff' for non-integer and negative scalar arguments, or for
      computing many binomial coefficients at once with vector inputs
      for N or K.
 
-     See also: bincoeff, perms
+     See also: bincoeff, perms.
 @end example
 @noindent
-using info, whereas in a printed documentation using @TeX{} it will
-appear as
+whereas in printed documentation using @TeX{} it will appear as
 
 @deftypefn  {Function File} {@var{c} =} nchoosek (@var{n}, @var{k})
 @deftypefnx {Function File} {@var{c} =} nchoosek (@var{set}, @var{k})
 
-Compute the binomial coefficient or all combinations of a set of items.
+Compute the binomial coefficient of @var{n} or list all possible
+combinations of a @var{set} of items.
 
 If @var{n} is a scalar then calculate the binomial coefficient
 of @var{n} and @var{k} which is defined as
-
 @tex
 $$
  {n \choose k} = {n (n-1) (n-2) \cdots (n-k+1) \over k!}
                = {n! \over k! (n-k)!}
 $$
 @end tex
-
 @noindent
 This is the number of combinations of @var{n} items taken in groups of
 size @var{k}.
@@ -665,10 +665,10 @@
 @end group
 @end example
 
-@code{nchoosek} works only for non-negative, integer arguments.  Use
-@code{bincoeff} for non-integer and negative scalar arguments, or for
-computing many binomial coefficients at once with vector inputs for @var{n}
-or @var{k}.
+Programming Note: When calculating the binomial coefficient @code{nchoosek}
+works only for non-negative, integer arguments.  Use @code{bincoeff} for
+non-integer and negative scalar arguments, or for computing many binomial
+coefficients at once with vector inputs for @var{n} or @var{k}.
 
 @seealso{bincoeff, perms}
 @end deftypefn

--- a/scripts/specfun/nchoosek.m	Fri Aug 29 13:27:36 2014 -0700
+++ b/scripts/specfun/nchoosek.m	Fri Aug 29 16:30:11 2014 -0700
@@ -21,7 +21,8 @@
 ## @deftypefn  {Function File} {@var{c} =} nchoosek (@var{n}, @var{k})
 ## @deftypefnx {Function File} {@var{c} =} nchoosek (@var{set}, @var{k})
 ##
-## Compute the binomial coefficient or all combinations of a set of items.
+## Compute the binomial coefficient of @var{n} or list all possible
+## combinations of a @var{set} of items.
 ##
 ## If @var{n} is a scalar then calculate the binomial coefficient
 ## of @var{n} and @var{k} which is defined as
@@ -75,10 +76,10 @@
 ## @end group
 ## @end example
 ##
-## @code{nchoosek} works only for non-negative, integer arguments.  Use
-## @code{bincoeff} for non-integer and negative scalar arguments, or for
-## computing many binomial coefficients at once with vector inputs
-## for @var{n} or @var{k}.
+## Programming Note: When calculating the binomial coefficient @code{nchoosek}
+## works only for non-negative, integer arguments.  Use @code{bincoeff} for
+## non-integer and negative scalar arguments, or for computing many binomial
+## coefficients at once with vector inputs for @var{n} or @var{k}.
 ##
 ## @seealso{bincoeff, perms}
 ## @end deftypefn
@@ -87,16 +88,17 @@
 ## Author: Paul Kienzle <pkienzle@users.sf.net>
 ## Author: Jaroslav Hajek
 
-function A = nchoosek (v, k)
+function C = nchoosek (v, k)
 
   if (nargin != 2
-      || !isnumeric (k) || !isnumeric (v)
-      || !isscalar (k) || ! (isscalar (v) || isvector (v)))
+      || ! (isreal (k) && isscalar (k))
+      || ! (isnumeric (v) && isvector (v)))
     print_usage ();
   endif
-  if (k < 0 || k != fix (k)
-      || (isscalar (v) && (v < k || v < 0 || v != fix (v))))
-    error ("nchoosek: args are non-negative integers with V not less than K");
+  if (k < 0 || k != fix (k))
+    error ("nchoosek: K must be an integer >= 0");
+  elseif (isscalar (v) && (iscomplex (v) || v < k || v < 0 || v != fix (v)))
+    error ("nchoosek: N must be a non-negative integer >= K");
   endif
 
   n = length (v);
@@ -104,39 +106,39 @@
   if (n == 1)
     ## Improve precision at next step.
     k = min (k, v-k);
-    A = round (prod ((v-k+1:v)./(1:k)));
-    if (A*2*k*eps >= 0.5)
-      warning ("nchoosek", "nchoosek: possible loss of precision");
+    C = round (prod ((v-k+1:v)./(1:k)));
+    if (C*2*k*eps >= 0.5)
+      warning ("nchoosek: possible loss of precision");
     endif
   elseif (k == 0)
-    A = zeros (1,0);
+    C = zeros (1,0);
   elseif (k == 1)
-    A = v(:);
+    C = v(:);
   elseif (k == n)
-    A = v(:).';
+    C = v(:).';
   elseif (k > n)
-    A = zeros (0, k, class (v));
+    C = zeros (0, k, class (v));
   elseif (k == 2)
     ## Can do it without transpose.
     x = repelems (v(1:n-1), [1:n-1; n-1:-1:1]).';
     y = cat (1, cellslices (v(:), 2:n, n*ones (1, n-1)){:});
-    A = [x, y];
+    C = [x, y];
   elseif (k < n)
     v = v(:).';
-    A = v(k:n);
+    C = v(k:n);
     l = 1:n-k+1;
     for j = 2:k
-      c = columns (A);
-      cA = cellslices (A, l, c*ones (1, n-k+1), 2);
+      c = columns (C);
+      cA = cellslices (C, l, c*ones (1, n-k+1), 2);
       l = c-l+1;
       b = repelems (v(k-j+1:n-j+1), [1:n-k+1; l]);
-      A = [b; cA{:}];
+      C = [b; cA{:}];
       l = cumsum (l);
       l = [1, 1 + l(1:n-k)];
     endfor
-    clear cA b;
-    A = A.';
+    C = C.';
   endif
+
 endfunction
 
 
@@ -145,14 +147,19 @@
 %!assert (size (nchoosek (1:5,0)), [1 0])
 
 %% Test input validation
-%!warning nchoosek (100,45);
+%!error nchoosek ()
+%!error nchoosek (1)
+%!error nchoosek (1,2,3)
+
+%!error nchoosek (100, 2i)
+%!error nchoosek (100, [2 3])
 %!error nchoosek ("100", 45)
-%!error nchoosek (100, "45")
-%!error nchoosek (100, ones (2,2))
-%!error nchoosek (repmat (100, [2 2]), 45)
-%!error nchoosek (100, -45)
-%!error nchoosek (100, 45.5)
-%!error nchoosek (100, 145)
-%!error nchoosek (-100, 45)
-%!error nchoosek (100.5, 45)
+%!error nchoosek (100*ones (2, 2), 45)
+%!error <K must be an integer .= 0> nchoosek (100, -45)
+%!error <K must be an integer .= 0> nchoosek (100, 45.5)
+%!error <N must be a non-negative integer .= K> nchoosek (100i, 2)
+%!error <N must be a non-negative integer .= K> nchoosek (100, 145)
+%!error <N must be a non-negative integer .= K> nchoosek (-100, 45)
+%!error <N must be a non-negative integer .= K> nchoosek (100.5, 45)
+%!warning <possible loss of precision> nchoosek (100, 45);