Draw a Graph in C# using zedGraph

Question

Hello,
I need to create a graph that have the following properties:
The X Axis is for schools names.
The Y Axis is for classes names.
In Point (x,y) I need to put a dot that it's color will represent the number of students (darker means more students).
I'm using ZedGraph (using that sample: http://zedgraph.org/wiki/index.php?title=Gradient-By-Value_Demo), but I don't know how to put the dot (and to determine it's dark-level) in the correct position (compare it to school's name and class's name).
Also, I don't know how to make the X and Y axis to show the school's name and the class's name.
How can I do that? (It's NOT have to be in zedGraph).
many thanks!

Answer 1

Hi, I don't do quite this in my project, but I do change the color based on some criteria. It should be pretty easy for you to modify. Look at the svn depot in stochfit.sourceforge.net at the graphing classes. You may also want to take a look at the version of zedgraph I have in my depot, some image capture and a scaling bug were fixed.

Answer 2

The problem is that ZedGraph is treating a Text-type scale in a little bit strange way. So it's almost impossible to display correctly data when you have both scales of Text type.

But you can fool ZG a little bit.

The whole trick is to display the data using coordinates of hidden scale, while displaying second, fake scale.

string[] schools = { "A", "B", "C" };
string[] classes = { "cl. 1", "cl. 2", "cl. 3" };

var pane = zg1.GraphPane;
Random x = new Random();

// Hide the basic scale, show the second with text labels
pane.X2Axis.Type = AxisType.Text;
pane.X2Axis.IsVisible = true;
pane.Y2Axis.Type = AxisType.Text;
pane.Y2Axis.IsVisible = true;
pane.XAxis.Scale.IsVisible = false;
pane.YAxis.Scale.IsVisible = false;

pane.X2Axis.Scale.TextLabels = schools;
pane.Y2Axis.Scale.TextLabels = classes;

// Main problem - synchronize the scales correctly            
pane.XAxis.Scale.Min = -0.5;
pane.XAxis.Scale.Max = schools.Count() - 0.5;
pane.YAxis.Scale.Min = -0.5;
pane.YAxis.Scale.Max = classes.Count() - 0.5;

pane.YAxis.MajorGrid.IsZeroLine = false;

// generate some fake data
PointPairList list = new PointPairList();
   for(int i=0;i<schools.Count();i++)
      for (int j = 0; j < classes.Count(); j++)
      {
          list.Add(new PointPair(i, j, x.Next(30)));
      }

   var pointsCurve = pane.AddCurve("", list, Color.Transparent);
   pointsCurve.Line.IsVisible = false;
   // Create your own scale of colors.
   pointsCurve.Symbol.Fill = new Fill(new Color[] { Color.Blue, Color.Green, Color.Red });
   pointsCurve.Symbol.Fill.Type = FillType.GradientByZ;
   pointsCurve.Symbol.Fill.RangeMin = 0;
   pointsCurve.Symbol.Fill.RangeMax = 30;
   pointsCurve.Symbol.Type = SymbolType.Circle;

            pane.AxisChange();
            zg1.Refresh();