Drawing an outline around one data point in heatmap

Specific Domains Visualization
,
1

Suppose I have a heatmap created using Makie.jl:

data = rand(10,10)

fig = Figure()
ax = Axis(fig[1,1], aspect=1)
hm = heatmap!(ax, data)

fig

The heatmap is essentially 10x10 rectangles with different colors. How do I draw a rectangle around the rectangle of a specified data point, e.g. at (x,y)=(3,3)?

Using something like scatter!(ax, 3, 3, marker=:rect, color=:black) doesn’t quite work because it’s hard to control the markersize and more importantly the symbol is filled, masking the color of the heatmap data point. I just want to draw an outline around the data point.

2

Don’t draw a symbol, draw a polygon (rectangle) with the wished coordinates.

3

You can do wireframe!(ax, Rect2f(origin, widths)) or BBox(left, right, bottom, top) (alternative Rect constructor.