Need Random Calc within 1-8 Range

[Bob476]

I'm trying to create a field that will calculate a non-unique random number between a given range (1-8) for each record.

That is, each record out of 125, for example, would each have a random value between 1 and 8 for that field.

Solutions?

[-Queue-]

Truncate( Random* 7.1, 0 ) + 1

Adding 1 prevents 0 from being an option. Using 7.1 ensures adding 1 and truncating won't exceed 8.

[CobaltSky]

If you require that the numbers be truly random (and therefore evenly distributed over a large sample) using 7.1 will not do, as it will ensure that the numbers 1 to 7 occur in the result with a frequency ten times that of the number 8. To achieve a random distribution of numbers from 1 to 8, I suggest you use:

Int(Random * 8) + 1

The Random function produces a number between zero and 1 (not inclusive). Since it will never equal either 0 or 1, multiplying it by 8 will produce a result which extends from 0.0000000000000001 to 7.99999999999999 (once the floating point limitation of 15 decimal places in FMP v6 is applied to it).

Applying Int( ) to this result will give an even distribution of integers from 0 to 7 inclusive, and only then will adding one give you the result you've asked for.

[-Queue-]

Well dang, it was nice of FM to include that little detail regarding exclusivity in their help file. Luckily I haven't had need to use random numbers in my business.

I assume then, that Truncate(Random* 8, 0) + 1 would be satisfactory and similar to Int(Random* 8) + 1, though minorly more complex.

[CobaltSky]

-Queue- said:

Well dang, it was nice of FM to include that little detail regarding exclusivity in their help file. Luckily I haven't had need to use random numbers in my business.

Yes. If it were inclusive, an unweighted distribution of results could be appropximated using Int(Random * 7.999) + 1. Not only is the online help entry on the Random function implicit rather than explicit, but the example it cites also contains several errors.

I assume then, that Truncate(Random* 8, 0) + 1 would be satisfactory and similar to Int(Random* 8) + 1, though minorly more complex.

Yep. Modestly over-engineered, but nonetheless effective...