Hi,

I would like to generate 2 unique random numbers between 1 and 4. i..e 
random 1 = any random number between 1 and 4 = rand(1, 4)
random 2 = any random number between 1 and 4, other than random 1.

could you suggest me a solution?

Here is a JavaScript solution - forums.limesurvey.org/forum/can-i-do-thi...dnumber-twice#191558

Hi,
I saw in the linked thread "No EM solution".

Here is one:
1. equation (rand1) {if(is_empty(rand1,rand(1,4),rand1)}  - the usual way to create a random number.
2. equation (base2) {str_replace(rand1,"","1234")} - remove the first random number from this string
3. equation (rand2) {if(is_empty(rand2),substr(base2,rand(0,2),1),rand2)} - select randomly one character from the remaining string.

Now rand1 and rand2 are two different random numbers.

Just to show that it is possible.
Of course, this only works with numbers between 1 and 9.
Else it has to be more sophisticated.

Joffm

And there is an one-equation solution.

If you consider that there are only 6 (4 over 2) different combinations
1-2, 1-3, 1-4, 2-3, 2-4, 3-4

one random number between 1 and 6 is sufficient

And the questions than get the relevance equations:
Q1: random < 4
Q2: random==1 or random==4 or random==5
Q3: random==2 or random==4 or random==6
Q4: random= or random>4

This is to show that remembering a bit of mathematics at school some things may become easy.

Joffm

PS.
Of course I know that this gets very complicated when trying to select 3 out of 10. (10 over 3 = 120)

Show off!

I can't spell mathamatics.