Related to #4550, I noticed this doesn't produce quite the expected output. The issue is that Extent defines the range of cell CENTERS or CORNERS (depending on alignment), but I think many people who manually set Extent want to define the edges of the heatmap. I'll use this issue to track renaming Extent to Rectangle and figuring how how to achieve a more commonly expected result.

// create a heatmap of any size
double[,] data = {
    { 1, 2, 3 },
    { 4, 5, 6 },
    { 7, 8, 9 },
};

// add the heatmap to the plot
var hm = myPlot.Add.Heatmap(data);

// place the heatmap in a rectangle defined in coordinate space
hm.Extent= new CoordinateRect(-5, 5, -5, 5);

ISSUE: I'd expect the heatmap edges to go to -5 and +5 on both axes