Best way to generate random number between two sets of values

Question

I need to generate a random number that's between -40 and -10 and 10 and 40. So the results could be 25, but never -5 or 5.

I've looked online, but the solutions seem overly complex. Is there any way to do it in just one or two lines?

Answer 1

Math.random() will return a random number between 0 and 1.

Create your own function to create a random number between your min and max numbers. Scale a random number between your min and max, then offset by you min value.

function randomBetween(min, max) {
  return Math.random() * (max - min) + min;
}

Answer 2

Generate a number between 10 and 40 and then generate a 1 or 0, if 0 convert it to negative 1 and multiply by either result Math.random() * 30 + (Math.random() < 0.5 ? -40 : 10);

Answer 3

That's 62 distinct values, 31 in each subrange, so:

r = Math.floor(Math.random()*62);
if (r < 31) { r -= 40; } else { r -= 21; }

Answer 4

var n = Math.random()*62;
return n - (n < 31 ? 40 : 21);

Answer 5

for(int i=15;i<=46;i++)
{
    double random=Math.rand()*5+i; 
    int rand=(int)random;
    System.out.println(rand);

}

The above code generates the random number between 15-50

Math.random()*5=i  

This gives the lower value i.e 15 here in this case

Note: you need to subtract 4 from the upper bond of the value i.e here if u use i<=50 this will be printing no up to 54 , similarly if you want to generate no. b/w 50-80 use (int i=50;i<=76;i++)

hope this helped :)

Answer 6

Short Answer:
It could be tricky but definitely the best way is to write your own function.

var random = (Math.random() - 0.5) * 2;

if (random >= 0){
    random = lerp(10, 40, random);
} else {
    random = lerp(-40, -10, Math.abs(random));
}

function lerp (min, max, value){
    return (1 - value) * min + value * max;
}    

Explanation:

There are (3) three steps you need to follow in order to achieve what you need.

1. A random number (between -1 and 1).

   let random = (Math.random() - 0.5) * 2
   

2. An if condition to know if the value is negative or positive.

   if (random >= 0){ /* Is Positive */ }
   else { /* Is Negative */ }
   

3. Lerp between the values you need (-40 to-10 if negative or 10 to 40 if positive).

   // This function interpolates between two numbers based on a normalized value (between 0 and 1)
   function lerp (min, max, value){
      return (1 - value) * min + value * max;
   }
   
   

Answer 7

The algorithm is (rand*(max-min))+min

Math.floor(Math.random()*30)+10

and

Math.floor(Math.random()*-30)-10