Can anyone help, I'm trying to create some test data, eg 1000 rows in excel. In each cell a formula (?) returns some text such as Dog, Cat or Rabbit based on the probability Dog=0.5, Cat=0.3, Rabbit=0.2
I've come up with a messy solution of generating a random number between 1-100 and then using a lookup table where 1-50 = dog etc... it works but is long winded and difficult for other people to follow.
Last edited by JP2008; 02-10-2009 at 03:15 PM.
I think this worksI tried on 3000 cells and got
=IF(RAND()>0.5,"Dog",IF(AND(RAND()>0.2,RAND()<=0.5),"Cat","Rabbit"))Does this work for you?Cat 20 Dog 51 Rabbit 29
ChemistB
My 2?
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Hi, thanks for the formula.
The logic of the formula looks 100% correct but the cat & rabbit results come out the wrong way round. Its something to do with the random function which appears 3 times in the formula, perhaps Excel recalculates as it steps through the formula.
To test this I took the rand() function out of the calculation and put it into cell D1 so there could only be one random number in each row.
Changing the formula to
=IF(D1>0.5,"Dog",IF(AND(D1>0.2,D1<=0.5),"Cat","Rabbit"))
This does return 500 dog, 300 cat and 200 rabbit
Strange.Oh well, your method will work just fine.
um.. Yea it does work. the Rand() will return a different number every time it's called, so yes you need to call it only once. The trick of using the cell refference seems to work. Though I suppose there is a better way.
However, What I wanted to point out is one thing.
While that does work, it can be shortened.=IF(D1>0.5,"Dog",IF(AND(D1>0.2,D1<=0.5),"Cat","Rabbit"))
If the D1 is greater than 0.5, you'll get dog. If it isn't, then we go to second if.=IF(D1>0.5,"Dog",IF(D1>0.2,"Cat","Rabbit"))
If D1 is greater than 0.2 we don't need to test if it's less than or equal to 0.5 cause that was done b y the first IF. So we just return Cat. And if it's not greater than 0.2 then return Rabbit.
=LOOKUP(RAND(), {0,0.5,0.8}, {"Dog","Cat","Rabbit"})
Entia non sunt multiplicanda sine necessitate
Nice Shg! I keep forgetting the lookup function. ::Smacks head::::
Hi. Sorry to dredge up an old thread.
I was looking to do exactly as the thread describes and found Shg's solution to work nicely. However...
...
How could I make this work by referencing cells instead of hard-coding them into the formula? I have quite a lengthy list of probabilities and outcomes!
Should work nicely with a VLOOKUP
=VLOOKUP(RAND(), $A$2:$B$10, 2)
with lower percentile limits in A2:A10 and results in B2:B10
Works very nicely.
Thanks!
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