How to graph a CSV file in VB

Question

Hi, so I have a CSV file in my working directory and dont know how to load in into a graph in VB. I already loaded my chart into the form and its called "Chart1" with "Series1".
The CSV has the following structure:
Date Value1 Value2
27/04/2012 45.1 60.1
26/04/2012 45.2 60.2.. ..
I cant figure out how to extract this data from the "*.csv" file and put in it a graph where the
Date is the x axis and the
Value2 is the y axis.
Any code would be greatly appreciated!

Answer 1

Is the CSV file data in reverse date order?  Your example includes only two lines, so the sequence is not clear.
If so, then you want to add the items to the series by working from the end of the file towards the beginning of the file. That would plot the points along the x-axis in order of increasing date.  Is that correct?
But then you say that you want to plot from the beginning to a certain date. Do you mean that you want to plot (reversed) from the beginning of the file to a certain nominated ending date? Or do you want to plot the items starting at the end of the file
and working backwards through the file so that the plot starts at a nominated starting date?  I have assumed the former.
To adjust the above code for these new requirements you should load the data into an object that you can manipulate to your requirements.  Then you need to separate the plotting from the file access.  A list is more suitable than an array.
Dim Readings As List(Of Reading) = New List(Of Reading)
Dim StartDate As Date = New Date(2012, 4, 24)
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim CurrentPoint As Integer = 0
Using MyReader As New Microsoft.VisualBasic.FileIO.TextFieldParser("C:\Users\Public\Readings.txt")
MyReader.TextFieldType = Microsoft.VisualBasic.FileIO.FieldType.Delimited
MyReader.Delimiters = New String() {","}
Dim currentRow As String()
While Not MyReader.EndOfData
Try
currentRow = MyReader.ReadFields()
Dim D As String = currentRow(0)
Try
Dim Y As Double = CDbl(currentRow(2))
Readings.Add(New Reading(D, Y))
Catch ex As InvalidCastException
If CurrentPoint <> 0 Then
MsgBox("Item " & currentRow(2) & " is invalid. Skipping")
End If
End Try
Catch ex As Microsoft.VisualBasic.FileIO.MalformedLineException
If CurrentPoint <> 0 Then
MsgBox("Line " & ex.Message & " is invalid. Skipping")
End If
End Try
End While
End Using
Readings.Reverse()
CurrentPoint = 0
Chart1.Series(0).Points.Clear()
For Each R As Reading In Readings
Dim D As Date = CDate(R.Read_Date)
If D >= StartDate Then
Chart1.Series(0).Points.AddY(R.Read_Data)
Chart1.Series(0).Points(CurrentPoint).AxisLabel = R.Read_Date
CurrentPoint += 1
End If
Next
End Sub
That code uses the following class:
Public Class Reading
Public Read_Date As String
Public Read_data As Double
Public Sub New(ByVal Item1 As String, ByVal item2 As Double)
Read_Date = Item1
Read_data = item2
End Sub
End Class
I know this thread is a couple years old but I tried this code and it works in Studio 2013 Community and it is very close to what I need. I want to make it a line chart and I want to have 4 series- Temp, Temp_SP, RH% and RH%_SP so I can log some trending
data from an environmental chamber at work. Can someone help me out with this?
Thanks,
Dan