Solved

Choosing every Nth record to create a "random sample"

Posted on 2013-01-28
5
1,048 Views
Last Modified: 2013-01-29
Is there a way to chose every Nth record in Crystal Reports?  I need to perform an audit where I need to generate a sample population from over 22,000 records.  I would like to create a formula  that only displays every 35th record in order to create a sample size of closer to 640.  I need a sample from all parts of the records, so the Nth percentile, or Nth smallest or largest wont work.  I have done similiar things in Excel, but I am asked to do this a lot and I would like to do it in Crystal with out exporting it.  Any help would be appreciated.  I am using Crystal Reports XI.
0
Comment
Question by:josslmpd
5 Comments
 
LVL 18

Expert Comment

by:vasto
ID: 38829221
Better do this on the database side. Then instead of 22000 records you will download just ~600. Your report will be 35 times faster. What is your database type?
0
 

Author Comment

by:josslmpd
ID: 38829239
It is a SQL server database.  I was hoping to do it in crystal since I am already running a selection fromula against the data to get it to the 22000 records.
0
 
LVL 3

Expert Comment

by:contactnaeem
ID: 38829540
Best option to do this at database level but if your requirement is at report level then you can hide or show records based on evaluation formula. Have a look at below link

http://msdn.microsoft.com/en-us/library/ms225351(v=vs.80).aspx
0
 
LVL 77

Assisted Solution

by:peter57r
peter57r earned 250 total points
ID: 38830127
To suppress everything except every 35th record you just put this into the Suppress conditional format button in the Section Expert.

Recordnumber mod 35 <>0
However, if the report contains any standard  summary totals they will still include  ALL of records meeting the record selection criteria  (they will not change to reflect the reduced number of records actually displayed).  If you want totals to be correct you will have to change the way they are calculated.
0
 
LVL 22

Accepted Solution

by:
Ido Millet earned 250 total points
ID: 38830696
Here's an FAQ I wrote about this many years ago:

Displaying a Random Sample
faq767-3260

If you need to randomly select and display a given number of records, or a user-specified proportion of the records, here's a simple approach:

Step 1:  
Place the following formula (@Random_Number)
in the detail section:
---------------
Rnd()
---------------

Step 2:
Sort the records by @Random_Number  (ascending).

Step 3:
In the suppress attribute of the detail section enter the following expression:

3.1 If you need to display a given number of Records:
----------------------------------------
RecordNumber > {?Show_N_Records}
----------------------------------------
where {?Show_N_Records} is a parameter allowing the user to
specify the number of records to be shown.

3.2 If you need to display a given proportion of Records:
----------------------------------------
RecordNumber > ({?Show_X_Percent}/100) * Count({some_field})
----------------------------------------
where {?Show_X_Percent} is a parameter allowing the user to
specify a number between 0 and 100.

Cheers,
- Ido
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

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

Suggested Solutions

Crystal Reports: 5 Tests for Top Performance It is complete, your masterpiece report.  Not only does it meet your customer’s expectations, it blows them out the water, all they want is beautifully summarised and displayed in a myriad of ways. …
There have always been a lot of questions related to when Crystal Reports evaluates report components (such as formulas, summaries, cross-tabs, charts, to name a few examples). Crystal Reports uses a two-pass reporting process to provide greater …
Here's a very brief overview of the methods PRTG Network Monitor (https://www.paessler.com/prtg) offers for monitoring bandwidth, to help you decide which methods you´d like to investigate in more detail.  The methods are covered in more detail in o…
The Email Laundry PDF encryption service allows companies to send confidential encrypted  emails to anybody. The PDF document can also contain attachments that are embedded in the encrypted PDF. The password is randomly generated by The Email Laundr…

932 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

Need Help in Real-Time?

Connect with top rated Experts

10 Experts available now in Live!

Get 1:1 Help Now