Patch function gives crosses when multiple squares attempted

Trying to place four squares with patch gradients, code works when only doing one but when trying with multiple it produces X with left and right triangles. Coord order same as when works for single

shapesx=[0 5 5 0;0 5 5 0;5 10.5 10.5 5;5 10.5 10.5 5];
shapesy=[0 0 5 5;5 5 10.5 10.5;0 0 5 5;5 5 10.5 10.5];
shapesc=[0 2.5 5 2.5;2.5 5 7.5 5;2.5 5 7.5 5; 5 7.5 10 7.5];
patch(shapesx,shapesy,shapesc)

Answer 1

[Mike Garrity]

Yeah, this can be a bit confusing.

If you look at the help for the XYC form of patch, it says:

one polygon ("face") per column is added

So in this case:

shapesx=[0 5 5 0];
shapesy=[0 0 5 5];
shapesc=[0 2.5 5 2.5];
patch(shapesx,shapesy,shapesc)

We have 4 columns which each have 1 row. So in theory, we should get 4 1-sided polygons. But this is a special case. These 1x4 arrays are called "row vectors". If you give patch (and many other graphics commands) a row vector when it expects a "column vector", then it will transpose for you. So it's just as if you had done this:

patch(shapesx',shapesy',shapesc')

But in your 4x4 case, this special case doesn't apply. So in that case you do need to worry about the fact that each column is going to become a polygon, rather than each row.

So I think what you really want is this:

shapesx=[0 5 5 0;0 5 5 0;5 10.5 10.5 5;5 10.5 10.5 5];
shapesy=[0 0 5 5;5 5 10.5 10.5;0 0 5 5;5 5 10.5 10.5];
shapesc=[0 2.5 5 2.5;2.5 5 7.5 5;2.5 5 7.5 5; 5 7.5 10 7.5];
patch(shapesx',shapesy',shapesc')

or this:

shapesx=[0 0 5     5  ; ...
         5 5 10.5 10.5; ...
         5 5 10.5 10.5; ...
         0 0 5     5  ];
shapesy=[0 5    0  5   ; ...
         0 5    0  5   ; ...
         5 10.5 5  10.5; ...
         5 10.5 5  10.5];
shapesc=[0   2.5 2.5 5  ; ...
         2.5 5   5   7.5; ...
         5   7.5 7.5 10 ; ...
         2.5 5   5   7.5];
patch(shapesx,shapesy,shapesc)