Help with Math Plot, Graph, Curve

Question

I would like to make a graph drawer but I have no idea where to start from, so if anyone could recommend a method or seen a tutorial or found a project, I would really like to see. I would prefere to be in vb language.

Thanks

Answer 1

Hello Dim131,

Thanks for your post.

Sorry for the dalay. Check the following examples which about how to create chart or graph in VB.NET. Hope them helpful.

http://www.linglom.com/2010/05/11/creating-graph-with-vb-net-part-1-basic-chart/
(Creating Graph with VB.NET)
http://msdn.microsoft.com/en-us/beginner/bb308769.aspx
(Generate Charts and Graphs Using Visual Studio Express)

If you have any problems, please feel free to follow up.

Best regards,

Liliane

---

Please mark the replies as answers if they help and unmark them if they provide no help.
Welcome to the All-In-One Code Framework! If you have any feedback, please tell us. Thanks

Answer 2

Thanks for your help, but what I was looking for wasn't exactly that. I am looking for how I can enter a mathematical expression (with an x value) and the programme can plot it in the cartesian coordinates system

thanks,
Dimitris

Answer 3

I am sorry if this does not belong here I dont usally write just read. Dim131 I am having the same issues i am also very determined to find out how to plot points and I hope lines from my app that calculates slope intercept. If you do find a solution or have already please help me I will return the favor.

Answer 4

One way I have over come this problem is by working out all the possible "y" values if the graph comes in the form of "y=mx+c" at small intervals of of "x." This "small" interval of x will depend on your screen resolution and how accurate you the the graph to be. After this create an array of x values and y values. The y values will be generated by solving the equation of "y=mx+c." After this have a loop to "plot" the graph for you for each point within certain limit. This limit will depend on yours or the user's screen resolution. 

 

Please feel free to email me at: [e-mail] or you can visit my youtube channel on lionking422 or my website at: sagga.co.uk.

Answer 5

Hi,

Tell us if this code and explanation helps you.

When the program starts, it draws grid lines for the graph. When the user clicks the Graph button, the program checks the m_GraphThread object to see if the graphing thread is running. If m_GraphThread is Nothing, then the program creates the new thread, making its startup routine the DrawGraph subroutine. It sets the thread's priority to BelowNormal so it won't preempt the main program and starts the thread.

If the m_GraphThread object is not Nothing, then the program stops the thread.

 

Private m_GraphThread As Thread

' Start drawing the graph.
Private Sub btnGraph_Click(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles btnGraph.Click
    If m_GraphThread Is Nothing Then
        ' The thread isn't running. Start it.
        AddStatus("Starting thread")

        m_GraphThread = New Thread(AddressOf DrawGraph)
        m_GraphThread.Priority = ThreadPriority.BelowNormal
        m_GraphThread.IsBackground = True
        m_GraphThread.Start()

        AddStatus("Thread started")

        btnGraph.Text = "Stop"
    Else
        ' The thread is running. Stop it.
        AddStatus("Stopping thread")

        m_GraphThread.Abort()
        ' m_GraphThread.Join()
        m_GraphThread = Nothing

        AddStatus("Thread stopped")

        btnGraph.Text = "Start"
    End If
End Sub

 

When the new thread starts, it runs subroutine DrawGraph. This routine repeatedly calls subroutine NewValue to generate a value and PlotValue to plot the value. When the user clicks the Start button, the program aborts the thread and the thread's DrawGraph code catches an exception.

 

' Draw a graph until stopped.
Private Sub DrawGraph()
    Try
        ' Generate pseudo-random values.
        Dim y As Integer = m_Y
        Do
            ' Generate the next value.
            NewValue()

            ' Plot the new value.
            PlotValue(y, m_Y)
            y = m_Y
        Loop
    Catch ex As Exception
        AddStatus("[Thread] " & ex.Message)
    End Try
End Sub

 

Subroutine NewValue generates a random new value in a straightforward manner.

 

' Generate the next value.
Private Sub NewValue()
    ' Delay a bit before calculating the value.
    Dim stop_time As Date = Now.AddMilliseconds(20)
    Do While Now < stop_time
    Loop

    ' Calculate the next value.
    Static rnd As New Random
    m_Y += rnd.Next(-4, 5)
    If m_Y < 0 Then m_Y = 0
    If m_Y >= picGraph.ClientSize.Height - 1 Then m_Y = _
        picGraph.ClientSize.Height - 1
End Sub
`This is where you can write equation and mathematical stuffs to calculate values

 

Subroutine PlotValue is a bit odd. It cannot directly access the program's main form because controls (including the form) can only be modified by the thread that created them. PlotValue starts by checking the InvokeRequired property. If InvokeRequired is True, then the code is running on the thread so it must invoke the main UI thread. In that case, the code makes an array of parameters to pass to the main UI thread and invokes the main thread's PlotValue method. At this point, the main UI thread executes PlotValue. This time InvokeRequired returns False because we're running on the main UI thread. The program uses the Graphics object's DrawImage method to move the existing graph one pixel to the left and then draws the new value.

' Plot a new value.
Private Delegate Sub PlotValueDelegate(ByVal old_y As _
    Integer, ByVal new_y As Integer)
Private Sub PlotValue(ByVal old_y As Integer, ByVal new_y _
    As Integer)
    ' See if we're on the worker thread and thus
    ' need to invoke the main UI thread.
    If Me.InvokeRequired Then
        ' Make arguments for the delegate.
        Dim args As Object() = {old_y, new_y}

        ' Make the delegate.
        Dim plot_value_delegate As PlotValueDelegate
        plot_value_delegate = AddressOf PlotValue

        ' Invoke the delegate on the main UI thread.
        Me.Invoke(plot_value_delegate, args)

        ' We're done.
        Exit Sub
    End If

    ' Make the Bitmap and Graphics objects.
    Dim wid As Integer = picGraph.ClientSize.Width
    Dim hgt As Integer = picGraph.ClientSize.Height
    Dim bm As New Bitmap(wid, hgt)
    Dim gr As Graphics = Graphics.FromImage(bm)

    ' Move the old data one pixel to the left.
    gr.DrawImage(picGraph.Image, -1, 0)

    ' Erase the right edge and draw guide lines.
    gr.DrawLine(Pens.Blue, wid - 1, 0, wid - 1, hgt - 1)
    For i As Integer = m_Ymid To picGraph.ClientSize.Height _
        Step GRID_STEP
        gr.DrawLine(Pens.LightBlue, wid - 2, i, wid - 1, i)
    Next i
    For i As Integer = m_Ymid To 0 Step -GRID_STEP
        gr.DrawLine(Pens.LightBlue, wid - 2, i, wid - 1, i)
    Next i

    ' Plot a new pixel.
    gr.DrawLine(Pens.White, wid - 2, old_y, wid - 1, new_y)

    ' Display the result.
    picGraph.Image = bm
    picGraph.Refresh()

    gr.Dispose()
End Sub

This program's AddStatus subroutine adds a status message to the txtStatus TextBox. Because the TextBox was created by the main UI thread, the program must check InvokeRequired as before.

 

' Add a status string to txtStatus.
Private Delegate Sub AddStatusDelegate(ByVal txt As String)
Private Sub AddStatus(ByVal txt As String)
    ' See if we're on the worker thread and thus
    ' need to invoke the main UI thread.
    If Me.InvokeRequired Then
        ' Make arguments for the delegate.
        Dim args As Object() = {txt}

        ' Make the delegate.
        Dim add_status_delegate As AddStatusDelegate
        add_status_delegate = AddressOf AddStatus

        ' Invoke the delegate on the main UI thread.
        Me.Invoke(add_status_delegate, args)

        ' We're done.
        Exit Sub
    End If

    txtStatus.Text &= vbCrLf & txt
    txtStatus.Select(txtStatus.Text.Length, 0)
    txtStatus.ScrollToCaret()
End Sub

 

Notes: This example uses a Timer to update a label holding the current time. 
Because the graphing is performed on a separate thread, the Timer continues to 
operate while graphing is occurring. This example is a bit tedious to understand but here is it... Try this and you will succeed...!!

---

Thanks

Rehan Bharucha - The Tech Robot

MCTS, MCITP, MCPD, MCT

Answer 6

Hi,

Tell us if this code and explanation helps you.

When the program starts, it draws grid lines for the graph. When the user clicks the Graph button, the program checks the m_GraphThread object to see if the graphing thread is running. If m_GraphThread is Nothing, then the program creates the new thread, making its startup routine the DrawGraph subroutine. It sets the thread's priority to BelowNormal so it won't preempt the main program and starts the thread.

If the m_GraphThread object is not Nothing, then the program stops the thread.

 

Private m_GraphThread As Thread

' Start drawing the graph.
Private Sub btnGraph_Click(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles btnGraph.Click
    If m_GraphThread Is Nothing Then
        ' The thread isn't running. Start it.
        AddStatus("Starting thread")

        m_GraphThread = New Thread(AddressOf DrawGraph)
        m_GraphThread.Priority = ThreadPriority.BelowNormal
        m_GraphThread.IsBackground = True
        m_GraphThread.Start()

        AddStatus("Thread started")

        btnGraph.Text = "Stop"
    Else
        ' The thread is running. Stop it.
        AddStatus("Stopping thread")

        m_GraphThread.Abort()
        ' m_GraphThread.Join()
        m_GraphThread = Nothing

        AddStatus("Thread stopped")

        btnGraph.Text = "Start"
    End If
End Sub

 

When the new thread starts, it runs subroutine DrawGraph. This routine repeatedly calls subroutine NewValue to generate a value and PlotValue to plot the value. When the user clicks the Start button, the program aborts the thread and the thread's DrawGraph code catches an exception.

 

' Draw a graph until stopped.
Private Sub DrawGraph()
    Try
        ' Generate pseudo-random values.
        Dim y As Integer = m_Y
        Do
            ' Generate the next value.
            NewValue()

            ' Plot the new value.
            PlotValue(y, m_Y)
            y = m_Y
        Loop
    Catch ex As Exception
        AddStatus("[Thread] " & ex.Message)
    End Try
End Sub

 

Subroutine NewValue generates a random new value in a straightforward manner.

 

' Generate the next value.
Private Sub NewValue()
    ' Delay a bit before calculating the value.
    Dim stop_time As Date = Now.AddMilliseconds(20)
    Do While Now < stop_time
    Loop

    ' Calculate the next value.
    Static rnd As New Random
    m_Y += rnd.Next(-4, 5)
    If m_Y < 0 Then m_Y = 0
    If m_Y >= picGraph.ClientSize.Height - 1 Then m_Y = _
        picGraph.ClientSize.Height - 1
End Sub
`This is where you can write equation and mathematical stuffs to calculate values

 

Subroutine PlotValue is a bit odd. It cannot directly access the program's main form because controls (including the form) can only be modified by the thread that created them. PlotValue starts by checking the InvokeRequired property. If InvokeRequired is True, then the code is running on the thread so it must invoke the main UI thread. In that case, the code makes an array of parameters to pass to the main UI thread and invokes the main thread's PlotValue method. At this point, the main UI thread executes PlotValue. This time InvokeRequired returns False because we're running on the main UI thread. The program uses the Graphics object's DrawImage method to move the existing graph one pixel to the left and then draws the new value.

' Plot a new value.
Private Delegate Sub PlotValueDelegate(ByVal old_y As _
    Integer, ByVal new_y As Integer)
Private Sub PlotValue(ByVal old_y As Integer, ByVal new_y _
    As Integer)
    ' See if we're on the worker thread and thus
    ' need to invoke the main UI thread.
    If Me.InvokeRequired Then
        ' Make arguments for the delegate.
        Dim args As Object() = {old_y, new_y}

        ' Make the delegate.
        Dim plot_value_delegate As PlotValueDelegate
        plot_value_delegate = AddressOf PlotValue

        ' Invoke the delegate on the main UI thread.
        Me.Invoke(plot_value_delegate, args)

        ' We're done.
        Exit Sub
    End If

    ' Make the Bitmap and Graphics objects.
    Dim wid As Integer = picGraph.ClientSize.Width
    Dim hgt As Integer = picGraph.ClientSize.Height
    Dim bm As New Bitmap(wid, hgt)
    Dim gr As Graphics = Graphics.FromImage(bm)

    ' Move the old data one pixel to the left.
    gr.DrawImage(picGraph.Image, -1, 0)

    ' Erase the right edge and draw guide lines.
    gr.DrawLine(Pens.Blue, wid - 1, 0, wid - 1, hgt - 1)
    For i As Integer = m_Ymid To picGraph.ClientSize.Height _
        Step GRID_STEP
        gr.DrawLine(Pens.LightBlue, wid - 2, i, wid - 1, i)
    Next i
    For i As Integer = m_Ymid To 0 Step -GRID_STEP
        gr.DrawLine(Pens.LightBlue, wid - 2, i, wid - 1, i)
    Next i

    ' Plot a new pixel.
    gr.DrawLine(Pens.White, wid - 2, old_y, wid - 1, new_y)

    ' Display the result.
    picGraph.Image = bm
    picGraph.Refresh()

    gr.Dispose()
End Sub

This program's AddStatus subroutine adds a status message to the txtStatus TextBox. Because the TextBox was created by the main UI thread, the program must check InvokeRequired as before.

 

' Add a status string to txtStatus.
Private Delegate Sub AddStatusDelegate(ByVal txt As String)
Private Sub AddStatus(ByVal txt As String)
    ' See if we're on the worker thread and thus
    ' need to invoke the main UI thread.
    If Me.InvokeRequired Then
        ' Make arguments for the delegate.
        Dim args As Object() = {txt}

        ' Make the delegate.
        Dim add_status_delegate As AddStatusDelegate
        add_status_delegate = AddressOf AddStatus

        ' Invoke the delegate on the main UI thread.
        Me.Invoke(add_status_delegate, args)

        ' We're done.
        Exit Sub
    End If

    txtStatus.Text &= vbCrLf & txt
    txtStatus.Select(txtStatus.Text.Length, 0)
    txtStatus.ScrollToCaret()
End Sub

 

Notes: This example uses a Timer to update a label holding the current time. 
Because the graphing is performed on a separate thread, the Timer continues to 
operate while graphing is occurring. This example is a bit tedious to understand but here is it... Try this and you will succeed...!!

 

---

Thanks

 

Rehan Bharucha - The Tech Robot

MCTS, MCITP, MCPD, MCT

Hi Sir,

There was a slight mistake in the above code.

First thing, assign a white background picture to the picturebox picgraph

Set the gridstep variable to the desired gap in between the grid lines horrizontal here i have chosen 3

Take up a windows application and copy paste the code with controls button named as btnGraph textbox as txtStatus and picturebox as picGraph, set the form background color as white, picturebox default image to white and run the application after pasting this code entirely without changing the name of the form.

 

Imports System.Threading

Public Class Form1
    Private m_GraphThread As Thread
    Private m_Y As Integer

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

    End Sub

    ' Start drawing the graph.
    Private Sub btnGraph_Click(sender As System.Object, e As System.EventArgs) Handles btnGraph.Click
        If m_GraphThread Is Nothing Then
            ' The thread isn't running. Start it.
            AddStatus("Starting thread")

            m_GraphThread = New Thread(AddressOf DrawGraph)
            m_GraphThread.Priority = ThreadPriority.BelowNormal
            m_GraphThread.IsBackground = True
            m_GraphThread.Start()

            AddStatus("Thread started")

            btnGraph.Text = "Stop"
        Else
            ' The thread is running. Stop it.
            AddStatus("Stopping thread")

            m_GraphThread.Abort()
            ' m_GraphThread.Join()
            m_GraphThread = Nothing

            AddStatus("Thread stopped")

            btnGraph.Text = "Start"
        End If

    End Sub

    ' Draw a graph until stopped.
    Private Sub DrawGraph()
        Try
            ' Generate pseudo-random values.
            Dim y As Integer = m_Y
            Do
                ' Generate the next value.
                NewValue()

                ' Plot the new value.
                PlotValue(y, m_Y)
                y = m_Y
            Loop
        Catch ex As Exception
            AddStatus("[Thread] " & ex.Message)
        End Try
    End Sub

    ' Generate the next value.
    Private Sub NewValue()
        ' Delay a bit before calculating the value.
        Dim stop_time As Date = Now.AddMilliseconds(20)
        Do While Now < stop_time
        Loop

        ' Calculate the next value.
        Static rnd As New Random
        m_Y = rnd.Next(10, 100)
        If m_Y < 0 Then m_Y = 0
        If m_Y >= picGraph.ClientSize.Height - 1 Then m_Y = _
            picGraph.ClientSize.Height - 1
    End Sub

    Private Delegate Sub PlotValueDelegate(ByVal old_y As Integer, ByVal new_y As Integer)

    Private Sub PlotValue(ByVal old_y As Integer, ByVal new_y As Integer)
        ' See if we're on the worker thread and thus
        ' need to invoke the main UI thread.
        If Me.InvokeRequired Then
            ' Make arguments for the delegate.
            Dim args As Object() = {old_y, new_y}

            ' Make the delegate.
            Dim plot_value_delegate As PlotValueDelegate
            plot_value_delegate = AddressOf PlotValue

            ' Invoke the delegate on the main UI thread.
            Me.Invoke(plot_value_delegate, args)

            ' We're done.
            Exit Sub
        End If

        ' Make the Bitmap and Graphics objects.
        Dim wid As Integer = picGraph.ClientSize.Width
        Dim hgt As Integer = picGraph.ClientSize.Height
        Dim bm As New Bitmap(wid, hgt)
        Dim gr As Graphics = Graphics.FromImage(bm)
        Dim m_Ymid As Integer
        Dim GRID_STEP As Integer = 10
        'Top left corner is considered as 0

        ' Move the old data one pixel to the left.
        gr.DrawImage(picGraph.Image, -1, 0)

        ' Erase the right edge and draw guide lines.
        gr.DrawLine(Pens.Blue, wid - 1, 0, wid - 1, hgt - 1)
        For i As Integer = m_Ymid To picGraph.ClientSize.Height Step GRID_STEP
            gr.DrawLine(Pens.LightBlue, wid - 2, i, wid - 1, i)
        Next i
        For i As Integer = m_Ymid To 0 Step -GRID_STEP
            gr.DrawLine(Pens.LightBlue, wid - 2, i, wid - 1, i)
        Next i

        ' Plot a new pixel.
        gr.DrawLine(Pens.White, wid - 2, old_y, wid - 1, new_y)

        ' Display the result.
        picGraph.Image = bm
        picGraph.Refresh()

        gr.Dispose()
    End Sub

    ' Add a status string to txtStatus.
    Private Delegate Sub AddStatusDelegate(ByVal txt As String)
    Private Sub AddStatus(ByVal txt As String)
        ' See if we're on the worker thread and thus
        ' need to invoke the main UI thread.
        If Me.InvokeRequired Then
            ' Make arguments for the delegate.
            Dim args As Object() = {txt}

            ' Make the delegate.
            Dim add_status_delegate As AddStatusDelegate
            add_status_delegate = AddressOf AddStatus

            ' Invoke the delegate on the main UI thread.
            Me.Invoke(add_status_delegate, args)

            ' We're done.
            Exit Sub
        End If

        txtStatus.Text &= vbCrLf & txt
        txtStatus.Select(txtStatus.Text.Length, 0)
        txtStatus.ScrollToCaret()
    End Sub

End Class

This application when run produces the result by automated plotting of graph based on random values in the function NewValue where you can also put equation to calculate value for your Y axis (Your logic comes in this function).

 

The below image is when the application is run, the graph comes plotting from right side of screen scrolling towards the left of the screen, just like a eco cardiogram of a heart patient based on random values.

This is it!

I hope this might have solved a bit of your concern. Dont forget to upvote it and mark as answer if it helps you even a bit..

 

 

---

Thanks

 

Rehan Bharucha - The Tech Robot

MCTS, MCITP, MCPD, MCT