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/qmr.m
+++ b/scripts/sparse/qmr.m
@@ -98,7 +98,7 @@
     elseif (isa (A, "function_handle"))
       Ax  = @(x) feval (A, x, "notransp");
       Atx = @(x) feval (A, x, "transp");
-    elseif (ismatrix (A))
+    elseif (isnumeric (A) && ismatrix (A))
       Ax  = @(x) A  * x;
       Atx = @(x) A' * x;
     else
@@ -124,7 +124,7 @@
     elseif (isa (M1, "function_handle"))
       M1m1x  = @(x) feval (M1, x, "notransp");
       M1tm1x = @(x) feval (M1, x, "transp");
-    elseif (ismatrix (M1))
+    elseif (isnumeric (M1) && ismatrix (M1))
       M1m1x  = @(x) M1  \ x;
       M1tm1x = @(x) M1' \ x;
     else
@@ -142,7 +142,7 @@
     elseif (isa (M2, "function_handle"))
       M2m1x  = @(x) feval (M2, x, "notransp");
       M2tm1x = @(x) feval (M2, x, "transp");
-    elseif (ismatrix (M2))
+    elseif (isnumeric (M2) && ismatrix (M2))
       M2m1x  = @(x) M2  \ x;
       M2tm1x = @(x) M2' \ x;
     else