[RESOLVED] [2005] Bar Graphs

My teacher gradebook program keeps up with student grades for for quarters of the school year. I'd like to have a tab in the program that will display a bar graph/histogram of the grades for the whole class - for each quarter.

Something like this.

A********* 38%
B***** 21%
C****** 25%
D** 8%
F** 8%

But it might look nicer if there's a control that can do this sort of thing. Kind of like a progress bar. Basically, I want to get a quick picture of how the student averages look.

I'm thinking of just drawing colored boxes for the bars. Or maybe use a progress bar. Or possibly even just text characters like above.

The school year has 4 quarters so I'd like to make this fit neatly on one tabPage. I might also like to have this function for individual grades.

I don’t know any control that can be used to show a graph but there could be one. What do you want the graph to look like? A circle divided with different colors? Vertical or horizontal bars?

If you want the graph to be bars then you can easily draw them on the form or use label control or any other with different colors.

If you want the graph to be a circle shape then here is an example of it:

vb Code:

Public Class Form1
 
    Dim A As Single = 0.38F
    Dim B As Single = 0.21F
    Dim C As Single = 0.25F
    Dim D As Single = 0.08F
    Dim F As Single = 0.08F
 
    Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
        Dim startAngle, sweepAngle As Single
        'Draw the A
        startAngle = 270.0F
        sweepAngle = 360.0F * A
        e.Graphics.FillPie(Brushes.Green, New Rectangle(40, 40, 100, 100), startAngle, sweepAngle)
        'Draw the B
        startAngle += sweepAngle
        sweepAngle = 360.0F * B
        e.Graphics.FillPie(Brushes.Blue, New Rectangle(40, 40, 100, 100), startAngle, sweepAngle)
        'Draw the C
        startAngle += sweepAngle
        sweepAngle = 360.0F * C
        e.Graphics.FillPie(Brushes.Yellow, New Rectangle(40, 40, 100, 100), startAngle, sweepAngle)
        'Draw the D
        startAngle += sweepAngle
        sweepAngle = 360.0F * D
        e.Graphics.FillPie(Brushes.Violet, New Rectangle(40, 40, 100, 100), startAngle, sweepAngle)
        'Draw the F
        startAngle += sweepAngle
        sweepAngle = 360.0F * F
        e.Graphics.FillPie(Brushes.Red, New Rectangle(40, 40, 100, 100), startAngle, sweepAngle)
    End Sub
End Class

Assuming I go with circle graphs, how hard would it be to also print them on paper? I know that bar graphs made from text would be easy to print. Not sure about graphics stuff.

Quote:

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Originally Posted by DroopyPawn

Assuming I go with circle graphs, how hard would it be to also print them on paper? I know that bar graphs made from text would be easy to print. Not sure about graphics stuff.

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It won’t be difficult. All you need is to get the bitmap of the graph so that you can print it or do what ever with it. Here, I updated the code so that it draws the graph in a bitmap. Since you have the bitmap you can print it on the paper.

vb Code:

Public Class Form1
 
    Dim A As Single = 0.38F
    Dim B As Single = 0.21F
    Dim C As Single = 0.25F
    Dim D As Single = 0.08F
    Dim F As Single = 0.08F
    Dim myBitmap As Bitmap
 
    Private Sub DrawGraphButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DrawGraphButton.Click
 
        Dim bmp As New Bitmap(200, 200)
        Dim g As Graphics = Graphics.FromImage(bmp)
        Dim startAngle, sweepAngle As Single
        'Draw the A        
        startAngle = 270.0F
        sweepAngle = 360.0F * A
        g.FillPie(Brushes.Green, New Rectangle(0, 0, bmp.Width, bmp.Height), startAngle, sweepAngle)
        'Draw the B        
        startAngle += sweepAngle
        sweepAngle = 360.0F * B
        g.FillPie(Brushes.Blue, New Rectangle(0, 0, bmp.Width, bmp.Height), startAngle, sweepAngle)
        'Draw the C        
        startAngle += sweepAngle
        sweepAngle = 360.0F * C
        g.FillPie(Brushes.Yellow, New Rectangle(0, 0, bmp.Width, bmp.Height), startAngle, sweepAngle)
        'Draw the D        
        startAngle += sweepAngle
        sweepAngle = 360.0F * D
        g.FillPie(Brushes.Violet, New Rectangle(0, 0, bmp.Width, bmp.Height), startAngle, sweepAngle)
        'Draw the F        
        startAngle += sweepAngle
        sweepAngle = 360.0F * F
        g.FillPie(Brushes.Red, New Rectangle(0, 0, bmp.Width, bmp.Height), startAngle, sweepAngle)
        g.Dispose()
        myBitmap = bmp
    End Sub
End Class

I wonder how hard it would be to create a custom control that would build a bar graph with 5 bars. I could set it's "StudentCount" property to tell it how many students. Then set it's ACount property to tell how many As. BCount for number of students with B,s and so on. The control would then figure the percents and draw the bars in it's paint method.

Of course, I have no idea how to do all that.

Woohoo! I created a control to do what I want. I used a set of PictureBox controls with the BackgroundColor properties set to a blue color. All I have to send the control is a value for the number of grades (ACount, BCount, CCount, DCount, FCount) and it figures the percents for me then makes the PictureBoxes (the bars) the correct length.

Now I'll think about making it scalable based on how big I draw the control on my form.

One issue I haven't figured out yet... I want the StudentCount property to be ReadOnly but I had to set it in code inside the control. Therefore, I had to make it readable and writable to work. Any tips on that one?

Any ideas on what might be the easiest way to scale the bars horizontally so that the longest one alway gets really close to the right end of the control?

For example, in the attached picture, I entered the same data as in the picture above but I multiplied the length of each bar by 3. Multiplying by 3 will not work in every case but in this case it does show what I'm after. My scaling code would need to work for any set of numbers.

You can set a constant length for all the picture boxes, let say Width = 100. Then you calculate the persentige of each grade by deviding the total students count by grade count. For example if you have 10 students and three of them got "A" then the percentige for "A" would be 3/10 = 0.3 which is the percentige of the "A" grade. Then you multiply the constant Width = 100 by 0.3 wich = 30 and assing it to the "Width of the pictureBox. In this way the pictureBox Width will never be more than 100.

I got this...

vb Code:

pBiggestPercent = pAPercent
        If pBPercent > pBiggestPercent Then pBiggestPercent = pBPercent
        If pCPercent > pBiggestPercent Then pBiggestPercent = pCPercent
        If pDPercent > pBiggestPercent Then pBiggestPercent = pDPercent
        If pFPercent > pBiggestPercent Then pBiggestPercent = pFPercent
If pBiggestPercent > 0 Then pMultiplier = 100 / pBiggestPercent Else pMultiplier = 0

to work with this...

Private Sub lblPercent_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lblAPercent.TextChanged, lblBPercent.TextChanged, lblCPercent.TextChanged, lblDPercent.TextChanged, lblFPercent.TextChanged
Dim lblPercent As Label = DirectCast(sender, Label)
Dim w As Integer = Val(lblPercent.Text)

vb Code:

Select Case lblPercent.Name
            Case "lblAPercent"
                Me.pbA.Width = w * pMultiplier
            Case "lblBPercent"
                Me.pbB.Width = w * pMultiplier
            Case "lblCPercent"
                Me.pbC.Width = w * pMultiplier
            Case "lblDPercent"
                Me.pbD.Width = w * pMultiplier
            Case "lblFPercent"
                Me.pbF.Width = w * pMultiplier
        End Select
 
        UpdateStudentCount()
    End Sub

I am not sure what are you tring to achive with this code. I don't know what the pMultiplier contains and what is it for. Why you need to get the bigist percentige? Read my previuse post again. This task is very simple staff.

I wanted the bars to be scalable. If I make the Control.Width = 1000, then the bars are still only 100 or less in width. By finding the BiggestPercent, I can stretch that one all the way across the control and scale the others in a similar way.

Anyhow, I got it working that way. So I can have short bars or really long ones depending on the size of the control itself.

please could some one tell me is there any way how to display bargraphs in a datagrid or list view

Make several bitmaps of bars (different lengths) and set the cell's picture property to whichever bar you need maybe?

actually i wanted the same thing what you have done in a datagrid which displays the datas and their graphs in their repective cells

is there a method to do this ???

There's always a way to do it. But I wouldn't know what to do on this one.