Solved

The Infamous TDIST & TINV

Posted on 2007-11-20
8
2,265 Views
Last Modified: 2013-11-27
Hi everyone,

I have been tasked to create a tool using MS Access with VBA that performs a large number of calculations which involve the TDIST and TINV functions in excel. They perform the T-Distribution and Inverse T-Distribution.
The problem I have is that although they are functions in excel, they are not functions in Visual Basic.
My current work around solution is attached.

This has been working fine up until now, as i have not been dealing with the number of records i currently need to go through and can only run through around 2 records a second (as there are a large number of calulations to do per record).

My questions is:
Does anyone have the mathematical Public Function for calculating the TDIST and TINV available? Or if there is a speedier solution that the one I have linked below? Hopefully around 10 to 20 times quicker.

Thanks for your Time,

James
Public Function jzTINV(intProb As Double, intFree As Double) As Double
 
' Calculates the Inverse T-Distribution using a work around. As the formula TINV is not in Visual Basic,
' and it is quite complex mathematics, i have created this work around.
' It is a little slow, but works (around 5 to 10 calcs a sec, depending on computer)
 
    Dim intOut As Double
    Dim objExcel As Object
    Dim objWorkbook As Object
    Dim objWorksheet As Object
 
    Set objExcel = CreateObject("Excel.Application")
    objExcel.Visible = False
    Set objWorkbook = objExcel.Workbooks.Add()
    Set objWorksheet = objWorkbook.Worksheets(1)
    objWorksheet.Activate
    objExcel.cells(1, 2) = intProb
    objExcel.cells(1, 3) = intFree
    objExcel.cells(1, 1) = "=TINV(b1,c1)"
    
    intOut = objExcel.cells(1, 1).Value
    jzTINV = intOut
    objWorkbook.Close False
    objExcel.Quit
End Function

Open in new window

0
Comment
Question by:EnvAgency
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 3
8 Comments
 
LVL 10

Accepted Solution

by:
LennyGray earned 300 total points
ID: 20318838
I would create a function  that the opens the instance of Excel, setting the workbook and worksheet and later closing the workbook and setting the object to nothing (Set objExcel = Nothing), which you are not doing and can eventually blow-out memory.

Then, within that function call another function that deletes the cells that you are using, passes the values of your current Access record, performs the calculation and returns the results.

In this way, you are not adding the overhead of creating an instance of Excel and the destroy the instance for every record that you perform calculations.

Good Luck !!!
0
 

Author Comment

by:EnvAgency
ID: 20319104
Thanks alot LennyGray,

Although it has reduced the amount of time from 2 records per sec to 10, it still isn't quick enough. I guess the public function versions of TINV and TDIST is the only solutions.

Wish there was a way to give you some Points, but i'd prefer to keep this open in hope of getting the public function. Sorry

Thanks again,

James
0
 
LVL 85

Assisted Solution

by:Rory Archibald
Rory Archibald earned 200 total points
ID: 20319158
Rather than using a worksheet, you can just create an applicaiton object (once) and then use:
objExcel.Worksheetfunction.TInv
 and
objExcel.Worksheetfunction.TDist

which ought to be quicker.
Regards,
Rory
0
MS Dynamics Made Instantly Simpler

Make Your Microsoft Dynamics Investment Count  & Drastically Decrease Training Time by Providing Intuitive Step-By-Step WalkThru Tutorials.

 
LVL 10

Expert Comment

by:LennyGray
ID: 20319195
James -

The points are not important. Solving your problem is. I was happy to at least improve performance five-fold!

How about sending the entire array of records to the spreadsheet and then importing the entire array back to Access?

In other words, populate all of the rows (instead of one at a time) and then import all of the results into a temporary table in Access.

Lenny
0
 

Author Comment

by:EnvAgency
ID: 20319228
rorya - Yeah that worked, for some reason i remember trying that before and it didn't hmm strange one.

Lenny - Thought about doign that originally, but the number of records may exceed 80k.

Thank you both for your input, I think I got enough now to sort it out.

Thanks again
0
 

Author Closing Comment

by:EnvAgency
ID: 31410086
Great help cheers,
it would of been nice to get the mathematical function some how, but the solutions provided have speed things up 10 times their amount so I'm happy as Larry :)

Cheers again
0
 

Author Comment

by:EnvAgency
ID: 20321005
Combining the above it increased the speed from 2 records a second to 25 records a second.... so thanks again :)
0
 
LVL 10

Expert Comment

by:LennyGray
ID: 20321508
Rory or James -

Could you post the final code that you used? I'd like to learn how you used objExcel.Worksheetfunction.TInv and objExcel.Worksheetfunction.TDist

Thanks,
Lenny
0

Featured Post

Ransomware-A Revenue Bonanza for Service Providers

Ransomware – malware that gets on your customers’ computers, encrypts their data, and extorts a hefty ransom for the decryption keys – is a surging new threat.  The purpose of this eBook is to educate the reader about ransomware attacks.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Preparing an email is something we should all take special care with – especially when the email is for somebody you may not know very well. The pressures of everyday working life stacked with a hectic office environment can make this a real challen…
In Part II of this series, I will discuss how to identify all open instances of Excel and enumerate the workbooks, spreadsheets, and named ranges within each of those instances.
This Micro Tutorial demonstrates how to create Excel charts: column, area, line, bar, and scatter charts. Formatting tips are provided as well.
Access reports are powerful and flexible. Learn how to create a query and then a grouped report using the wizard. Modify the report design after the wizard is done to make it look better. There will be another video to explain how to put the final p…

724 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question