極座標軸の目盛りは円で示され、それぞれ個別にラベルを付けることができます。

ScottPlot.Plot myPlot = new();

var polarAxis = myPlot.Add.PolarAxis();
polarAxis.Rotation = Angle.FromDegrees(-90);

double[] ticksPositions = { 5, 10, 15, 20 };
string[] tickLabels = { "A", "B", "C", "D" };
polarAxis.SetCircles(ticksPositions, tickLabels);

polarAxis.SetSpokes(count: 5, length: 22, degreeLabels: false);

myPlot.SavePng("demo.png", 400, 300);