Randomise Array

[didierj]

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Cheers :beer:

[Yair]

...in this case, using the third method in 7.0 with an array of 10,000 elements leaves 1300-1400 of the elements in their original locations, which is a rather large margin of error (13 percent). Since this method is based on the random number generator and the number is around this range every time I run the VI it seems reasonable to assume that this is a property of the random number generation which is reflected through using this method.

I asked the cryptographer friend I mentioned about this and he provided me an explanation which shows that this is not LV's fault. He said that we can discard the number of times an element is switched more than once back to its original position as statistically insignificant and just look at the number of elements which were never moved.

Then, he said that the formula for calculating the chance of an element not being chosen was defined as

which means that the larger n gets, the closer the result is to e^-1. Then, he said that the chance of a single element of our array NOT being chosen is ((x-1)/x)^2x (it can be chosen once in each selection and we select 2x numbers because we select 2 random elements in each iteration.

He also said that the formula shown earlier only gets to e at infinity, but it gets very close to e at a very early stage, so basically that equation will be very close to e for any number above a certain number (let's say 20 or 30). With some simple power math he showed that the expression I wrote is equal to e to the power of -2 which comes out to 0.136, which is the result I got and means that LV's random function is now cleared.