Combinations and Permutations:any one can help ....

[xoctan657]

hi evryone i want to know if there are any expression can give me a value lik this:

($CY)*($CY - 1)*($CY - 2)*($CY - 3)*($CY - 4).....................................($CY-{$NCY-1})

so if any one know please help ..........and thanks very much......................................

Edited March 20, 2009 by xoctan657

[stevenong]

Can you describe exactly what you're trying to do please? Why do you need that type of expression? What's the purpose? There might be other ways of doing what you want.

Cheers!

steven

[xoctan657]

Can you describe exactly what you're trying to do please? Why do you need that type of expression? What's the purpose? There might be other ways of doing what you want.

Cheers!

steven

i did what i wanted just a few minuts back but anyway it will be helpfull if there are like this expression:

if we have $NCY=6

so with $CY=5 it will give me this value: ($CY)*($CY - 1)*($CY - 2)*($CY - 3)*($CY - 4)

and for $CY=4 give : ($CY)*($CY - 1)*($CY - 2)*($CY - 3)

and for $CY=3 give : ($CY)*($CY - 1)*($CY - 2)

and ..................................like this

as in the Combination in the mathematics

http://en.wikipedia.org/wiki/Combination

Edited March 20, 2009 by xoctan657

[ranxerox]

so you need factorial. In python, assuming that the input is in the "tx" channel:

param = int(ch("tx"))
if param <= 1:
	return 1
fac = 1
for i in range(2,param+1):
	fac = fac * i
return fac

i did what i wanted just a few minuts back but anyway it will be helpfull if there are like this expression:

if we have $NCY=6

so with $CY=5 it will give me this value: ($CY)*($CY - 1)*($CY - 2)*($CY - 3)*($CY - 4)

and for $CY=4 give : ($CY)*($CY - 1)*($CY - 2)*($CY - 3)

and for $CY=3 give : ($CY)*($CY - 1)*($CY - 2)

and ..................................like this

as in the Combination in the mathematics

http://en.wikipedia.org/wiki/Combination