Click here to Skip to main content
Click here to Skip to main content
Go to top

"Grid Snaps to Value" - Implementation-detail of Autoscaling Chartcontrol

, 7 Jan 2008
Rate this:
Please Sign up or sign in to vote.
Compute "SnapValues" with minimum of fractional digits, useful in autoscaling Chart-control

Introduction

Finally I found an algorithm to compute that member of the number-sequence
{... 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, ...}, which is most close to a given number.

The Code

   ''' <returns>
   ''' the to Number closest member of the sequence {... 0.5, 1, 2, 5, 10,...}
   ''' </returns>
   Private Function GetSnapValue(ByVal Number As Double) As Double
      'Int(Math.Log10(Val)): Comma-Position ( negative for: 0 < Number < 1 )
      Dim DecimalRangeBottom As Double = 10 ^ Int(Math.Log10(Number))
      Dim Numb As Double
      Dim Prev As Double = DecimalRangeBottom
      'tests 2-fold, 5-fold, 10-fold of DecimalRangeBottom
      For Each Factor As Double In New Double() {2, 5, 10}
         Numb = Factor * DecimalRangeBottom
         If Numb >= Number Then Exit For
         Prev = Numb
      Next
      'choose from Numb or Prev the closer one
      If Numb - Number < Number - Prev Then
         Return Numb
      Else
         Return Prev
      End If
   End Function

A Test

   Public Sub Main()
      For I As Integer = -10 To 10
         Dim Numb As Double = 63 ^ (I * 0.23)
         Console.WriteLine(String.Format( _
            "Number: {0,-22}SnapValue: {1,-5}", Numb, GetSnapValue(Numb)))
      Next
      Console.ReadLine()
   End Sub

Outputs

Number: 7,26970413682593E-05  SnapValue: 5E-05
Number: 0,000188523312755006  SnapValue: 0,0002
Number: 0,000488892515887717  SnapValue: 0,0005
Number: 0,00126783201821641   SnapValue: 0,001
Number: 0,0032878352074914    SnapValue: 0,002
Number: 0,00852625599945599   SnapValue: 0,01 
Number: 0,0221109139541476    SnapValue: 0,02 
Number: 0,0573396477796245    SnapValue: 0,05 
Number: 0,148697390542496     SnapValue: 0,1  
Number: 0,38561300618949      SnapValue: 0,5  
Number: 1                     SnapValue: 1    
Number: 2,59327352539712      SnapValue: 2    
Number: 6,72506757752559      SnapValue: 5    
Number: 17,4399397053036      SnapValue: 20   
Number: 45,2265339222859      SnapValue: 50   
Number: 117,284773066139      SnapValue: 100  
Number: 304,151496924626      SnapValue: 200  
Number: 788,748024684536      SnapValue: 1000 
Number: 2045,43937062368      SnapValue: 2000 
Number: 5304,38376764334      SnapValue: 5000 
Number: 13755,7179931757      SnapValue: 10000

This is useful, e.g., for an auto-scaling ChartControl, to compute the positions of the orientation-lines that way, that the line-caption-numbers have minimum fractional digits.

Using the Code

It may look like this:

AutoscaleChart

AutoscaleChart_2.gif

Shown is the same chart in different sizes of the Chartcontrol. The control did a proper autoscale to fill the whole available space with the chart, and the gridlines use the plus of space to be computed in a higher precision.

No user-input is required to adapt the control to a completely different range of values:

AutoscaleChart_4.gif

That's All

Here on CodeProject are published much more powerful Chart-Controls than mine, but I haven't checked out whether there is one with that feature.

History

  • 7th January, 2008: Initial post

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Share

About the Author

Mr.PoorEnglish

Germany Germany
No Biography provided

Comments and Discussions

 
GeneralJust for compare Pinmemberkonikula6-Jan-10 22:11 
GeneralRe: Just for compare Pinmemberkonikula6-Jan-10 22:15 
GeneralMy vote of 2 PinmemberMember 368237126-Aug-09 12:33 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Mobile
Web01 | 2.8.140916.1 | Last Updated 7 Jan 2008
Article Copyright 2008 by Mr.PoorEnglish
Everything else Copyright © CodeProject, 1999-2014
Terms of Service
Layout: fixed | fluid