# How to add a round disk in a ListPlot?

This should be very easy, but I can't make it to work properly. I need to add a circular disk in the following ListPlot code:

dot[gamma_] := Disk[{gamma, gamma 5}, 0.25]

graph1[gamma_] := ListPlot[
Table[{x, gamma x^2},
{x, -4, 4, 0.5}
],
Frame -> True,
Ticks -> All,
GridLines -> Automatic,
GridLinesStyle -> Directive[GrayLevel[0.5], Dashed],
PlotRange -> All,
PlotStyle -> Thick,
Joined -> True,
Mesh -> None,
InterpolationOrder -> 4,
Epilog -> {Red, dot[gamma]}  (* This disk should stay circular, not oval! *)
]

graph1[-1]


Currently, the red disk is a deformed oval. I need it to stay circular, whatever the AspectRatio of the plot. What's wrong with this code?

• Add AspectRatio -> Automatic, or use Point instead of Disk. Commented Aug 26, 2023 at 15:44
• If the image aspect ratio does not equal the coordinate aspect ratio, then circles appears as ellipses. Commented Aug 26, 2023 at 15:45

Change to use Offset:

dot[gamma_] := Disk[{gamma, gamma 5}, Offset[{4, 4}]]


• What is the Offset in the Disk?
– Cham
Commented Aug 26, 2023 at 15:47
• Please change to {10,4} as an example to see the effect. Also press F1 for the doc page that has example(s).
– Syed
Commented Aug 26, 2023 at 15:49
• @Cham It's the radius. Look up Offset and Scaled, etc. It's a question of image coordinates vs. graphics coordinates....See docs for Plot > Options > Epilog > 2nd example. Commented Aug 26, 2023 at 15:49
• Is there a way to make the point size "absolute", i.e the same size on screen whatever the AspectRatio and whatever the PlotRange?
– Cham
Commented Aug 26, 2023 at 16:04
• Isn't it compliant with those two requirements already?
– Syed
Commented Aug 26, 2023 at 16:06