Efficient way to assign a value from another value

Hey guys, (i'm not new to UnityAnswers, just have a new username due to the QATO port)

OK, i have a script that places objects on a certain X co-ord

 objectCopy.transform.position.x = array[whichNumber];

the whichNumber variable obviously tells the objectCopy which array item to choose ( this is out of integers -7,-5,-3,-1 etc to 7 - so 8 positions. )

I have another line in the same method which does this;

 if ( whichNumber == -7 ) { whichType = 0; } else if ( whichNumber == -5) ...etc

and that goes on for the 8 position ( -7, -5, -3... etc.)

whichType is for the Instantiate of objectCopy which is an array of gameObjects...

so that if the object was placed at -7, whichType would be 0 meaning it'll place object 0 of the array at -7... object 1 of the array at -5 etc...

MY QUESTION - (finally, lol!)

Is my if... else if... else if... else if... the best way to assign whichType from whichNumber? i feel there should be a more efficient way, unless my noobishness is leading me astray and this is perfectly acceptable?

Thanks for the help guys and girls, another stepping stone for me!

Matty.