[RESOLVED] How do you make a pie chart

[Aest]

im trying to figure out how to make a pie chart to visualize statistics in my program. however ive never done anything in the graphics department for VB. i cant find to much on google on the subject and what i can i dont get or it doesnt work. can anybody show me a simplistic way to draw a pie chart please?

[LaVolpe]

Using simple VB methods, a crude pie chart can be created rather easily. The example below shows that.

Some notes
1) VB draws arcs counter-clockwise.
2) VB uses radians not angles, therefore, a conversion is needed
3) In the example below, I used 10 percentages which total to 100%, 10 pies. If you will be using the pie chart for similar purposes, you must ensure the total is never > 100%

Add a command button and picturebox. Make the picturebox the size of the circle/pie you desire
Then paste this code. I commented the code a bunch. Hopefully you can follow it easily

Private Sub Command1_Click()

    Dim midPt As Long, endPt As Double
    Dim angle As Double, startPt As Double
    Dim totalPct As Double, Radius As Long
    Dim x As Long
    
    Dim RadianRatio As Double
    Dim lGrayScaleColor As Long
    
    Dim samplePcts(9) As Double
    samplePcts(0) = 5: samplePcts(1) = 15
    samplePcts(2) = 20: samplePcts(3) = 15
    samplePcts(4) = 5: samplePcts(5) = 9
    samplePcts(6) = 10: samplePcts(7) = 12
    samplePcts(8) = 3: samplePcts(9) = 6
    
    ' to color the pies
    Picture1.FillStyle = vbSolid
    
    
    ' VB's arc draws counter-clockwise from W > N > E > S > W
    '           90
    '
    '   180             0/360
    '
    '           270
    
    ' VB uses radians not degrees. Following multiplied against angle = radians
    RadianRatio = (Atn(1) * 4) / 180
    
    ' set midpoint where circle will be centered around
    If Picture1.ScaleWidth > Picture1.ScaleHeight Then
        midPt = Picture1.ScaleHeight \ 2
    Else
        midPt = Picture1.ScaleWidth \ 2
    End If
    
    ' radius of the circle/arc
    Radius = midPt
    
    ' start on the 0 degree mark. Note we want -values and you can't get -0 but can get -360
    startPt = 360 * RadianRatio
    
    For x = 0 To 9 ' process the percentages which total to 100
    
        totalPct = totalPct + samplePcts(x)
        angle = (360 * totalPct) / 100
        
        endPt = angle * RadianRatio
    
        ' set the pie color (grayscale)
        lGrayScaleColor = x * 20
        Picture1.FillColor = RGB(lGrayScaleColor, lGrayScaleColor, lGrayScaleColor)

        ' vbWhite below is the outline color
        ' negative startpt & endpt values closes the arc vs opened arc
        Picture1.Circle (midPt, midPt), Radius, vbWhite, -startPt, -endPt
        
        startPt = endPt ' set next pie start pos to last pie's end pos
    
    Next
    
End Sub

[Aest]

thank you for your response. your code doesnt seem to work on my version of VB (visual basic 2008 express). i altered the code to draw on the form itself. however its buggy and i cant figure out why. it skips all but 2 of the slices. i imagine i buggered something up rewriting your code. here is my code and an attached pic of the pie

Private Sub Form3_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint

        Dim dblIncome, dblMonth, dblTransit, dblSelf, dblDaily, dblSum As Double

        dblMonth = CDbl(Form1.lblTotalMonth.Text)
        dblTransit = CDbl(Form1.lblTotalCar.Text)
        dblSelf = CDbl(Form1.lblTotalSelf.Text)
        dblDaily = CDbl(Form1.lblTotalOther.Text)
        dblIncome = CDbl(Form1.lblTotal.Text)

        If dblIncome < 0 Then
            dblIncome = 0
        End If

        dblSum = dblMonth + dblTransit + dblSelf + dblDaily + dblIncome

        dblIncome = (dblIncome / dblSum)
        dblMonth = (dblMonth / dblSum)
        dblTransit = (dblTransit / dblSum)
        dblSelf = (dblSelf / dblSum)
        dblDaily = (dblDaily / dblSum)

        Dim startPt, endPt, angle, totalPct As Double
        Dim intx, Radius As Integer
        Dim RadianRatio As Double

        Dim Percents(4) As Double
        Percents(0) = dblIncome
        Percents(1) = dblMonth
        Percents(2) = dblTransit
        Percents(3) = dblSelf
        Percents(4) = dblDaily

        Dim Colors(4) As Color
        Colors(0) = Color.Green
        Colors(1) = Color.Blue
        Colors(2) = Color.Cyan
        Colors(3) = Color.Gray
        Colors(4) = Color.Aqua

        RadianRatio = (3.14159265 / 180)
        startPt = 0
        Radius = 200

        For intx = 0 To 4

            Dim BrushColor As New Drawing.SolidBrush(Colors(intx))

            totalPct = totalPct + Percents(intx)
            angle = (360 * totalPct)

            endPt = angle * RadianRatio

            e.Graphics.FillPie(BrushColor, 185, 40, Radius, Radius, CInt(-startPt), CInt(-endPt))

            startPt = endPt

        Next

        lblIncomeStat.Text = FormatPercent(dblIncome)
        lblMonthlyStat.Text = FormatPercent(dblMonth)
        lblTransitStat.Text = FormatPercent(dblTransit)
        lblSelfStat.Text = FormatPercent(dblSelf)
        lblDailyStat.Text = FormatPercent(dblDaily)


    End Sub

[LaVolpe]

Sorry, I gotta bug out, not a .Net user.
I don't know how FillPie works. Though it looks very similar to VB6's Circle method.
I see you are using negative values though. And if you set startPt at zero, it can't be negative (no such thing as -0). Could that be the problem? Try starting startPt out as 360*RadianRatio

[Aest]

i changed startpt back to 360 * radianratio but it still has the same prob. what i dont understand is i set the first color to be green but it starts at blue. is it a problem in the design of the for loop?

[LaVolpe]

I can't really help that much as I'm not a .Net guy. But I don't think it is the loop necessarily. I just think the first pie isn't drawing. You may want to verify startPt and endPt. Also, are you sure CInt() should be used for the start/end points? I would think that would round/up down the decimal values? Again, I'm not familiar with the FillPie function

[Aest]

i didnt initially convert it to integer but option stict was having a problem with doubles in the fillpie method

[LaVolpe]

i didnt initially convert it to integer but option stict was having a problem with doubles in the fillpie method

Try singles, not doubles, per this MSDN link

Edited: Also ensure .Net's FillPie requires radians, just maybe, it requires degrees? Check your help files or search forum/google for FillPie

[Aest]

you know what, i got so involved with the graphics that thought didnt even occur to me. im getting a full cyan circle now but at least its a full circle. ill just fiddle around with this but hopefully this is in the right direction. thanks for all your help

[Aest]

yup i got it working now. now that i knew how to word it correctly i found out what i need on google. turns out the method is (brush, x coordinate, y coordinate, length, height, start angle, sweep angle). so the endpt was actually just 360 * percents(intx) and the startpt was startpt = startpt + angle. and of course what opened my eyes in the first place was the angle was in degrees. thanks so much for your help

[LaVolpe]

Glad you got it figured out. One of these days, soon maybe, I'll start to play with .Net and you'll be able to answer my questions

Don't forget to mark this resolved, if it is now resolved. Use the Thread Tools menu near the top of your first post above.