Is it possible to match two series of data in a chart from two different datasets in c# winforms

Question

I am working on a application to chart boards inspected and board with defects based on work order number. I realize after looking at the chart and comparing the actual data, th

Answer 1

This is a classic mistake when working with Chart controls.

They seem to do everything automagically right until you get a little closer and hit upon problems.

Here is the rule:

All Values, both X-Values and all Y-Values are internally stored as doubles.

If you feed in numbers all works fine. If you feed in any other data type you are heading for trouble somewhere down the line.

At first all seems to work and the stuff you feed into shows up nicely in the labels.

But when you want to use any advanced ability of the Chart, chances are it work work..

This can be something as simple as formatting the labels, which works with string formats only. If you want to use a number format you need to feed in numbers!

You are hitting upon the problem of matching up points in different series.

You have fed in the X-Values as strings and so the trouble starts as soon as the data points need matching beyond the order in which you add them.

You could feed them in precise order but you need to understand what happens..

Lets have a look behind the scenes..: If you use the debugger to look into the x-Values of your series' datapoints, you will be amazed to see that they all are 0! The strings you fed in, have gone into the labels, but the X-Values are all the result of the failed conversion to double, resulting in 0. This means all datapoint have the same X-Value!

You have two options:

• Either add them all in synch, all in the same order and the same number of points in all series.

• Use numbers for X-Values.

Your workOrder looks like a number; if it is you can use it, if you want to, but it will then spread out the data according to those numbers. Probably not a good idea. Instead you can assign each workorder an index and use this instead.

To create nice labels use the AxisLabel property for each data point!

It is easiest, imo to create a DataPoint first with values and axislabel and maybe tooltips and colors and whatnot and then add it to the points collection.

---

Now to let this sink in, have a look at this chart:

This is the code to create it:

private void Form1_Load(object sender, EventArgs e)
{
    Random R = new Random(1);
    List> misses = new List>();
    chart1.Series.Clear();

    for (int i = 0; i < 3; i++ )
    {
        Series s = new Series("S" + (i + 1));
        s.ChartType = SeriesChartType.Column;
        chart1.Series.Add(s);
    }

    chart1.ChartAreas[0].AxisX.Interval = 1;

    foreach(Series s in chart1.Series)
    {
        for (int i = 0; i < 30; i+=3)
        {
            if (R.Next(3) > 0) s.Points.AddXY(i, i+1);
            else misses.Add(new Tuple(s, i));
        }
    }

    foreach (Tuple m in misses)
    {
        if (m.Item1.Name == "S1") m.Item1.Points.AddXY(m.Item2 + "X", m.Item2 + 5);
        else m.Item1.Points.AddXY(m.Item2, m.Item2 + 5);
    }

    for (int i = 0; i < chart1.Series[0].Points.Count - 1; i++)
    {
        chart1.Series[0].Points[i].AxisLabel = chart1.Series[0].Points[i].XValue + "%";
    }
}

Let's have a look at the things that happen:

I first create three series and then fill a few points into them. However I randomly leave a few slots empty.

I store these in a List of Tuples, so I can later add them out of order.

And you can see that they all match up, except for the blue series 'S1'.

Can you see why?

I always use a nice number for the X-Values, but not for the missed points in the blues series, where I have attached an "X" to the number.

Now these points are added too, but all with an X-Value of 0 and so they all sit at position 0.

Note: Note that the above is not code you can use. It is code to study to learn about the data types of Chart values and the consequences of adding strings as X-Values!