Can anyone help me out what does sign(rand-0.5) command mean

1.Probability of X >0 if X= rand-0.5 2.Probability of X =1 if X= sign(rand-0.5) 3.Probability of X =-1 if X= sign(rand-0.5)

Answer 1

[Star Strider]

The ‘sign(rand-0.5)’ returns the sign (-1,0,1) of that result —

for k = 1:10
    r = rand
    X = sign(r-0.5)
end

r = 0.1812

X = -1

r = 0.5620

X = 1

r = 0.3196

X = -1

r = 0.6013

X = 1

r = 0.7162

X = 1

r = 0.7427

X = 1

r = 0.9730

X = 1

r = 0.6988

X = 1

r = 0.4561

X = -1

r = 0.5195

X = 1

.

[Mashrur Zawad]

Thanks got it.What about rand-0.5?What -0.5 signifies?Does it denote the maximum and minimum range of random numbers?

[Torsten]

You take a random number between 0 and 1 (that's what rand does).

Then you subtract 0.5 from this random number.

The result will be between -0.5 and 0.5 ( 0 - 0.5 and 1 - 0.5 are the extremes that can happen) with equal probability.

So the probability of getting a result > 0 (namely a result between 0 and 0.5) is equal to the probability of getting a result < 0 (namely between -0.5 and 0).

Can you now answer the question what the probability of getting a result > 0 is ?

Answer 2

[Atsushi Ueno]

Uniformly distributed random numbers - MATLAB rand (mathworks.com)

rand generates a uniformly distributed random number between 0 and 1.

So, rand-0.5 means random number between -0.5 and 0.5.

Sign function (signum function) - MATLAB sign (mathworks.com)

rand returns an array Y the same size as x, where each element of Y is:

• 1 if the corresponding element of x is greater than 0.
• 0 if the corresponding element of x equals 0.
• -1 if the corresponding element of x is less than 0.

So, sign(rand-0.5) usually outputs -1 or 1 like a result of coin toss.

It is extremely rare for sign(rand-0.5) to output 0

[Mashrur Zawad]

1.Probability of X >0 if X= rand-0.5 2.Probability of X =1 if X= sign(rand-0.5) 3.Probability of X =-1 if X= sign(rand-0.5)

Can you tell me how to solve this?

[Atsushi Ueno]

1. 50%
2. 50%
3. 50%

Do you mean you want exact probability?

I mean you need probability of sign(rand-0.5)==0 or not.