Generate random values between two set numbers

问题:

My task is to generate 5000 random numbers between -2 and 5 then count up how many of those values are between 2 and 3 This is what I have so far:

randNums=rand(1,5000); %Generate 5000 random values between 0 and 1

randNums=randNums*7-2; %Get those random values to be between -2 and 5

I understand that 7*1=7 and 0*7=0 so -2 from each = 7-2, but I do nut fully understand how to apply that again if the numbers were to be between 5,6 or -6 and 1.

回答1:

My problem interpretation

You have random numbers in the interval (0,1). But you require random numbers in (a,b).

Solution

You simply have to scale and shift your interval.

Scale the interval: The size/length of the interval (a,b) is b-a. To rescale the interval you have to multiply all your random values with b-a.

Shift the interval: When you have scaled the interval you have numbers in the interval (0,b-a). You simply shift all numbers by adding the number a to it. Which leads to random numbers in the interval (a,b).

回答2:

What you are referring to is called "Linear Interpolation". In some libraries it is called lerp and usually it's implemented

float lerp(float v0, float v1, float t) {
    return v0+(v1-v0)*t
}

So in your case v0 is -2, v1 is 7 and t is the value between 0 and 1 you want to interpolate.

回答3:

numbers = random('unif', -2, 5, 1, 1000);
count = sum(numbers > 2 & numbers < 3);