how do i generate random numbers in an interval?

Comments

• Publison Posts: 12,366

  2020-04-02 16:25

  There is a Random Number Generator in the OBEX:
  
  http://obex.parallax.com/object/498
  
• Publison Posts: 12,366

  2020-04-02 16:31

  Type "Random" in the upper right search box and it will bring up some threads about Random generation.
• Phil Pilgrim (PhiPi) Posts: 23,514

  2020-04-02 16:34

  Try this in your program:
  

  VAR
    long seed
  
  PUB random(lo, hi)
    return lo + ?seed // (hi - lo)
  

  
  It will return a random number between lo and hi - 1.
  
  -Phil
  
• Electrodude Posts: 1,621

  2020-04-02 19:32

  Phil Pilgrim (PhiPi) wrote: »

  Try this in your program:
  

  VAR
    long seed
  
  PUB random(lo, hi)
    return lo + ?seed // (hi - lo)
  

  
  It will return a random number between lo and hi - 1.
  
  -Phil

  
  Are you sure that's correct? Don't you need to strip the sign bit before the // in case the result of ?seed is negative? Otherwise, it will return numbers in the range (lo-(hi-lo+1), hi).
• JonnyMac Posts: 8,918

  2020-04-02 19:49

  Don't you need to strip the sign bit ...

  I do that in the prng object that I liberated from @Heater.

  pub randomize(lo, hi) 
  
  '' Return a random number between lo and hi (inclusive)
  
    return  (random >> 1) // ((hi - lo) + 1) + lo
  

  I also try to stick a call to the random() method in a loop so that the prng sequence is constantly being tumbled. The P2 does this for us, providing a new random # on every clock.

  spin

  spin

  jm_prng.spin

  3K

  jm_prng.spin 3.2K
• Phil Pilgrim (PhiPi) Posts: 23,514

  2020-04-02 20:20

  Electrodude wrote:

  Are you sure that's correct? Don't you need to strip the sign bit before the // in case the result of ?seed is negative? Otherwise, it will return numbers in the range (lo-(hi-lo+1), hi).

  You're correct, of course. Jon has it right.
  
  -Phil
• bluejay Posts: 131

  2021-02-09 02:47

  is there a way to randomize numbers from 1 to 70?
  Thanks
• JonnyMac Posts: 8,918

  2021-02-09 07:19

  @bluejay said:
  is there a way to randomize numbers from 1 to 70?
  Thanks

  In the post above there is discussion about the randomize() method from the attached object. It would go like this:

  rval := prng.randomize(1, 70)

  Easy peasy.
• tritonium Posts: 540

  2021-02-09 13:35

  Hi

  @bluejay said:
  is there a way to randomize numbers from 1 to 70?
  Thanks

  I wonder if you are asking for all the numbers 1 to 70 to be in a randomised order since getting a random number between 1 and 70 has already been explained.
  If that is the case then build an array with the numbers 1 to 70 in it and starting at array item 1, exchange it with another number in the array, range 1-70 generated using the randomise function, and work your way through the whole array.

  Dave