Fix Matlab incompatibility of "ismatrix" (bug #42422). * data.cc (isvector): new tests * data.cc (isrow): documentation improved, new tests * data.cc (iscolumn): documentation improved, new tests * data.cc (ismatrix): is matrix now only checks the dimension due to Matlab compatibility, documentation improved, new tests * accumarray.m: use more appropriate function, than ismatrix * gradient.m: use more appropriate function, than ismatrix * num2str.m: use more appropriate functions, than ismatrix * ntsc2rgb.m: use more appropriate function, than ismatrix * condest.m: use more appropriate function, than ismatrix * expm.m: use more appropriate function, than ismatrix * onenormest.m: use more appropriate function, than ismatrix * isocolors.m: use more appropriate function, than ismatrix * isonormals.m: use more appropriate function, than ismatrix * isosurface.m: use more appropriate function, than ismatrix * __errcomm__.m: use more appropriate function, than ismatrix * __interp_cube__.m: use more appropriate function, than ismatrix * __marching_cube__.m: use more appropriate function, than ismatrix * __stem__.m: use more appropriate function, than ismatrix * stairs.m: use more appropriate function, than ismatrix * validsetargs.m: use more appropriate functions, than ismatrix * unique.m: use more appropriate functions, than ismatrix * bicg.m: additional tests for numerical value * bicgstab.m: additional tests for numerical value * cgs.m: additional tests for numerical value * gmres.m: additional tests for numerical value * qmr.m: additional tests for numerical value

--- a/scripts/sparse/cgs.m
+++ b/scripts/sparse/cgs.m
@@ -76,7 +76,7 @@
 
     if (ischar (A))
       A = str2func (A);
-    elseif (ismatrix (A))
+    elseif (isnumeric (A) && ismatrix (A))
       Ax = @(x) A * x;
     elseif (isa (A, "function_handle"))
       Ax = @(x) feval (A, x);
@@ -97,7 +97,7 @@
       M1m1x = @(x) x;
     elseif (ischar (M1))
       M1m1x = str2func (M1);
-    elseif (ismatrix (M1))
+    elseif (isnumeric (M1) && ismatrix (M1))
       M1m1x = @(x) M1 \ x;
     elseif (isa (M1, "function_handle"))
       M1m1x = @(x) feval (M1, x);
@@ -109,7 +109,7 @@
       M2m1x = @(x) x;
     elseif (ischar (M2))
       M2m1x = str2func (M2);
-    elseif (ismatrix (M2))
+    elseif (isnumeric (M2) && ismatrix (M2))
       M2m1x = @(x) M2 \ x;
     elseif (isa (M2, "function_handle"))
       M2m1x = @(x) feval (M2, x);