C# Read string from CSV file and plot line graph

Question

Currently, I am able to read data from multiple CSV file and plot line graph using windows form application. However, now I need to plot a line graph based on a CSV file's section name (3rd column of csv file).

Modified/New CSV file: (Added the Section Name column)

Values,Sector,Name
5.55,1024,red
5.37,1536,red
5.73,2048,blue
5.62,2560,.blue
5.12,3072,.yellow
...

1. Based on the Section Name column, my line graph need to be plotted accordingly in a Single line and different sections must be plotted with different colors, including the legends shown at the side of the graph must be shown based on the different section names.
2. 1 csv file = 1 Series. But there are same section names in a csv file (csv file example shown above, e.g. red for the 1st 20lines). Same section names = same color. If I open 2 or more csv files = 2 Series. Each Series will have different colors due to different section names in the csv file.

I am quite new with programming, and would really appreciate someone could help me by editing from my code.

Thank you.

Answer 1

You can separate the data by the section column and use the section names as index into the Series collection instead of using i.

Best use the section name as the Series.Name. I suggest using a data class containing the two numbers and the string and collect them in a List<Dataclass>. Then create Series for the distinct sections. Then loop over them..

Here are a few code examples:

Define a class for your data:

public class Data3
{
    public int N1 { get; set;}
    public double N2 { get; set;}
    public string S1 { get; set;}

    public Data3(double n2, int n1, string s1)
    {
        N1 = n1; N2 = n2; S1 = s1;
    }
}

Pick your own names! Optional but always recommended: Add a nice ToString() overload!

Declare a class level varible:

  List<Data3> data = new List<Data3>();

During the read collect the data there:

  data.Add(new Data3(Convert.ToDouble(pieces[1]), Convert.ToInt32(pieces[0]), pieces[2]));

To plot the chart first create the Series:

 var sections= data.Select(x => x.S1).Distinct<string>();
 foreach (string s in sections)
          chart.Series.Add(new Series(s) { ChartType = SeriesChartType.Line });

Then plot the data; the series can be indexed by their Names:

 foreach (var d in data) chart.Series[d.S1].Points.AddXY(d.N1, d.N2);

I left out the nitty gritty of integrating the code into your application; if you run into issues, do show the new code by editing your question!

A few notes:

• When in doubt always create a class to hold your data

• When in doubt always choose classes over structures

• When in doubt always choose List<T> over arrays

• Always try to break your code down to small chunks with helpful names.

Example: To read all the data in a csv file create a function to do so:

public void AppendCsvToDataList(string file, List<Data3> list)
{
    if (File.Exists(file))
    {
        var lines = File.ReadAllLines(file);
        for (int l = 1; l < lines.Length; l++)
        {
            var pieces = lines[l].Split(',');
            list.Add(new Data3(Convert.ToInt32(pieces[1]),
                               Convert.ToDouble(pieces[0]), pieces[2]));
        }
    }
}

Answer 2

Updated code:

GraphDemo (Form):

    List<Read> rrList = new List<Read>();

    void openToolStripMenuItem_Click(object sender, EventArgs e)
    {
        OpenFileDialog ff = new OpenFileDialog();
        Read rr;

        ff.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.Desktop); //"C:\\";
        ff.Filter = "csv files (*.csv)|*.csv|All files (*.*)|*.*";
        ff.Multiselect = true;
        ff.FilterIndex = 1;
        ff.RestoreDirectory = true;

        if (ff.ShowDialog() == DialogResult.OK)
        {
            try
            {
                rrList.Clear();
                foreach (String file in ff.FileNames) //if ((myStream = ff.OpenFile()) != null)
                {
                    rr = new Read(file);
                    rrList.Add(rr); 
                }

                //Populate the ComboBoxes
                if (rrList.Count > 0)
                {
                    string[] header = rrList[0].header; //header of first file
                    xBox.DataSource = header; 
                    yBox.DataSource = header.Clone(); //without Clone the 2 comboboxes link together!
                }
                if (yBox.Items.Count > 1) yBox.SelectedIndex = 1; //select second item
            }
            catch (Exception err)
            {
                //Inform the user if we can't read the file
                MessageBox.Show(err.Message);
            }
        }
    }

    private void button1_Click(object sender, EventArgs e)
    {
        Plot.Draw(rrList, xBox, yBox, chart);
    }

class Read:

public class Read
{
    public int nLines { get; private set; }
    public int nColumns { get; private set; }
    public string[] header { get; private set; }
    public float[,] data { get; private set; }
    public string fileName { get; set; }
    public string[] section { get; private set; }

    public Read(string file)
    {
        string[] pieces;

        fileName = Path.GetFileName(file);  
        string[] lines = File.ReadAllLines(file); // read all lines
        if (lines == null || lines.Length < 2) return; //no data in file
        header = lines[0].Split(','); //first line is header
        nLines = lines.Length - 1; //first line is header
        nColumns = header.Length;

        //read the numerical data and section name from the file
        data = new float[nLines, nColumns - 1]; // *** 1 less than nColumns as last col is sectionName
        section = new string[nLines]; // *** 
        for (int i = 0; i < nLines; i++) 
        {
            pieces = lines[i + 1].Split(','); // first line is header
            if (pieces.Length != nColumns) { MessageBox.Show("Invalid data at line " + (i + 2) + " of file " + fileName); return; }
            for (int j = 0; j < nColumns - 1; j++)
            {
                float.TryParse(pieces[j], out data[i, j]); //data[i, j] = float.Parse(pieces[j]);
            }
            section[i] = pieces[nColumns - 1]; //last item is section
        }
    }

}

class Plot:

public class Plot
{
    //public Plot() { } //no constructor required as we use a static class to be called

    public static void Draw(List<Read> rrList, ComboBox xBox, ComboBox yBox, Chart chart) //***
    {
        int indX = xBox.SelectedIndex;
        int indY = yBox.SelectedIndex;

        chart.Series.Clear(); //ensure that the chart is empty
        chart.Legends.Clear();
        Legend myLegend = chart.Legends.Add("myLegend");
        myLegend.Title = "myTitle";

        //define a set of colors to be used for sections
        Color[] colors = new Color[] { Color.Black, Color.Blue, Color.Red, Color.Green, Color.Magenta, Color.DarkCyan, Color.Chocolate, Color.DarkMagenta }; 

        //use a Dictionary to keep iColor of each section
        // key=sectionName, value=iColor (color index in our colors array)
        var sectionColors = new Dictionary<string, int>();

        int i = 0;
        int iColor = -1, maxColor = -1;
        foreach (Read rr in rrList)
        {
            float[,] data = rr.data;
            int nLines = rr.nLines;
            int nColumns = rr.nColumns;
            string[] header = rr.header;

            chart.Series.Add("Series" + i);
            chart.Series[i].ChartType = SeriesChartType.Line;

            //chart.Series[i].LegendText = rr.fileName;
            chart.Series[i].IsVisibleInLegend = false; //hide default item from legend

            chart.ChartAreas[0].AxisX.LabelStyle.Format = "{F2}";
            chart.ChartAreas[0].AxisX.Title = header[indX];
            chart.ChartAreas[0].AxisY.Title = header[indY];

            for (int j = 0; j < nLines; j++)
            {
                int k = chart.Series[i].Points.AddXY(data[j, indX], data[j, indY]);
                string curSection = rr.section[j];
                if (sectionColors.ContainsKey(curSection))
                {
                    iColor = sectionColors[curSection];
                }
                else
                {
                    maxColor++;
                    iColor = maxColor; sectionColors[curSection] = iColor;
                }
                chart.Series[i].Points[k].Color = colors[iColor];
            }

            i++; //series#

        } //end foreach rr

        //fill custom legends based on sections/colors
        foreach (var x in sectionColors)
        {
            string section = x.Key;
            iColor = x.Value;
            myLegend.CustomItems.Add(colors[iColor], section); //new LegendItem()
        }
    }

}