How to Create an Array of Unique Random Numbers

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Article ID: 136420 - View products that this article applies to.
This article was previously published under Q136420
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SUMMARY

The FoxPro RAND() function returns a random number between 0 and 1. This article shows by example how to:

  • Create random numbers between 5 and 10.
  • Easily create an array of random numbers between any two integers.
  • Make the random numbers in an array unique.
The user-defined functions (UDFs) listed in this article demonstrate how.

MORE INFORMATION

Step-by-Step Example

  1. Create a program file called Myudf.prg that contains the following code:
       FUNCTION RANDOM
       *  Returns a random number between any 2 numbers.
       *  Syntax: =RANDOM(Lower Value, Higher Value)
       *  Example:  lnX=RANDOM(5,10)
       PARAMETER anLow,anHigh
       lnRnumber=INT((RAND()*(anHigh-anLow+1))+anLow)
       RETURN lnRnumber
    
       FUNCTION A_RANDOM
       *  Returns an array of random numbers between any 2 numbers.
       *  The array must already be defined
       *  Syntax:   =A_RANDOM(ArrayName,Lower Value, Upper Value)
       *  Example:  =A_RANDOM('gaMyarray',17,25)
       PARAMETER lcA_name,anLow,anHigh
       lnAlength=ALEN(&lcA_name)
       FOR lni=1 TO lnAlength
         &lcA_name(lni)=INT((RAND()*(anHigh-anLow+1))+anLow)
       ENDFOR
       RETURN &lcA_name
    
       FUNCTION U_RANDOM
       *  Returns an array of unique random numbers  between any 2 numbers.
       *  The array must already be defined
       *  Syntax:   =U_RANDOM(Array Name, Lower Value, Upper Value)
       *  Example:  =U_RANDOM('gaMyarray',1,10)
       PARAMETER lcA_name,anLow,anHigh
       lnAlength=ALEN(&lcA_name)
       IF lnAlength>anHigh-anLow
          lnAlength=anHigh-anLow+1
       ENDIF
       &lcA_name=.F.
       lni=1
       DO WHILE lni<=lnAlength
          lnRnumber=INT((RAND()*(anHigh-anLow+1))+anLow)
          llNextnum=.T.
          IF lnRnumber=anLow .OR. lnRnumber=anHigh
             DO CASE
             CASE lnRnumber=anLow
                lnK=1
                DO WHILE lnK>0
                   anLow=anLow+1
                   lnK=ASCAN(&lcA_name,anLow)
                ENDDO
             CASE lnRnumber=anHigh
                lnK=1
                DO WHILE lnK>0
                   anHigh=anHigh-1
                   lnK=ASCAN(&lcA_name,anHigh)
                ENDDO
             ENDCASE
          ELSE
             lnK=ASCAN(&lcA_name,lnRnumber)
             IF lnK>0
                llNextnum=.F.
             ENDIF
          ENDIF
          IF llNextnum
             &lcA_name(lni)=lnRnumber
             lni=lni+1
          ENDIF
       ENDDO
    						
  2. Save and Close Myudf.prg
  3. Test the functions:

    1. To print a single random number between 5 and 10, type the following in the Command window:
            SET PROCEDURE TO MYUDF.PRG
            ? RANDOM(5,10)
      								
    2. To populate an array with random numbers, type the following in the Command window:
            SET PROCEDURE TO MYUDF.PRG
            DIMENSION gaMyarray(10)
            =A_RANDOM('gaMyarray',1,10)
      								
    3. If you want to populate an array with unique random numbers, type the following in the Command window:
            SET PROCEDURE TO MYUDF.PRG
            DIMENSION gaMyarray(10)
            U_Random('gaMyarray',1,10)

Properties

Article ID: 136420 - Last Review: December 3, 2003 - Revision: 2.1
APPLIES TO
  • Microsoft Visual FoxPro 3.0 Standard Edition
  • Microsoft FoxPro 2.0
  • Microsoft FoxPro 2.5b for MS-DOS
  • Microsoft FoxPro 2.5a
  • Microsoft FoxPro 2.5b for MS-DOS
  • Microsoft FoxPro 2.6 for MS-DOS
  • Microsoft FoxPro 2.6a Standard Edition
  • Microsoft FoxPro 2.5b
  • Microsoft FoxPro 2.5a
  • Microsoft FoxPro 2.5b
  • Microsoft FoxPro 2.6 Standard Edition
  • Microsoft FoxPro 2.6a Standard Edition
  • Microsoft FoxPro 2.5b for Macintosh
  • Microsoft Visual FoxPro 2.5c for Macintosh
  • Microsoft FoxPro 2.6a Professional Edition for Macintosh
  • Microsoft FoxPro 2.6 for SCO/UNIX
Keywords: 
KB136420

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