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Getting a random sign

Hi all,

I want to get a randomly generated binary choice:  either -1 or 1.  This function does it, but is there is a 'nicer' way?

  private int getRandomSign() {
    if (Math.random() <= 0.5) return -1;
      else return 1;
    }
  }
0
Dawkins
Asked:
Dawkins
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2 Solutions
 
sudhakar_koundinyaCommented:
That is the nicer way :)
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girionisCommented:
Can you define "nicer"? Your code looks fine.
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girionisCommented:
Maybe you could do

 private int getRandomSign() {
    if (Math.random() < 0.5) return -1;
      else return 1;
    }
  }

since it can return a value equal to zero but never one.
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sudhakar_koundinyaCommented:
I haven't understand the difference between if (Math.random() < 0.5) return -1; and if (Math.random() <= 0.5) return -1;

both results gives the value less than one only.

Regards
Sudhakar
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DawkinsAuthor Commented:
>>>  Maybe you could do...

Good point, it should be < rather than <=. I'll change that

>>> Can you define "nicer"? Your code looks fine.

well basically I am teaching myself how to program in Java and know no Java programers in real life so have no one to ask "is this completely ridiculous", so I come here instead :)  By nicer I mean "more elegant, simpler, less code, there's already a java library function that does that" etc

Seems like I've already found the best way so I'll give it another 30 minutes to make sure and then give you two the points.
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Roger NeymanRetired Software Engineer, Author, TeacherCommented:

Here's another approach that may be closer to what you want:

private int getRandomSigh() {
    return (int) (Math.signum(0.5-Math.random())) ;
}

An additional note:  using "<= 0.5" favors -1  VERY slightly  since Math.random() returns values between 0 and .999...
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Roger NeymanRetired Software Engineer, Author, TeacherCommented:
There's a problem with my posted solution: there's a very slight chance it will return 0. If you can't live with that, here's an amendment:


private int getRandomSign() {
    int sign = (int) (Math.signum(0.5-Math.random())) ;
    return sign = 0 ? 1 : sign ;
}
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JakobACommented:
nice & short:

private int getRandomSign() {
    return (Math.random()<0.5) ? 1 : -1;                           // ?: operator same as in C
}

regards JakobA
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DawkinsAuthor Commented:
Thanks everyone, I'll keep it as I originally had it but put < 0.5 instead to ensure the split is exactly 50/50
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girionisCommented:
:)
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