Face to vertex data interpolation for patch interpolated colors

I make a patch like so:

>> patch('verticex',xyz,'faces',conn,'faceVertexCData',c,'faceColor','flat')

In this the following is true:

>> size(xyz)  == [nvertices, 3]
>> size(conn) == [nfaces, 4] % so these are quads
>> size(c,1)  == nfaces
>> size(c,2)  == 1;

Or in other words, I have one datavalue for the color per face and I let 'patch' figure out the color needed for each face using some colormap. This all works fine, however I want an interpolated shading (instead of flat) for the faces (and edges). It seems that I need one datavalue for the color per vertex for that, instead of one per face. Or, in other words, this must be true:

>> size(c,1) == nvertices

So the question is: is there an easy way to interpolate face data to vertex data? Of course I can think of complicated ways by first determining the center of each face, and then do a griddedinterpolant, or use a plethora of other ways. But I wondered if there is a more readymade solution for this.