Just so we're all clear what's going on here: all plot types where this is meaningful (all except box and histogram?) allow you to use x0 and dx as alternatives to an x array, and will create an inferred array [x0, x0+dx, x0+2*dx...] behind the scenes, as long as they can infer the length of that array. For 1D types, it uses the length of y, and for 2D types it uses the length of the corresponding dimension of z. Same goes for y0 and dy (for 1D types you must provide either x or y as an array otherwise there's no length to use!). If x is missing and either x0 or dx is missing as well, they default to x0=0, dx=1.

For 2D types, xtype and ytype are only relevant if an array is present and you DON'T want to use it... so typically just from the GUI.

That's at least how this is supposed to work, I wouldn't be surprised if there are some places this is broken...