Is the phrase "in function of" proper English?

I'm not sure if this is pure English, or just something I picked up as a direct translation from my native language (Dutch).

It applies to maths/computer terms.

An example usage would be:

X is created in function of Y.

Someone I know claims this is not English. He suggests I use

X is created with respect to Y.

instead. Please help me prove him wrong.

I don't think you're going to prove him wrong. :-) "In function of" definitely sounds wrong, even in a maths/computing context.

Perhaps you mean that X is created as a function of Y. In a computing context, X may be returned by the function Y.

How would you say it in Dutch, then? X wordt gemaakt in functie van Y? That doesn't sound right, so you probably mean something else. I'd say X is een functie van Y or the other way around (x=3y is not as common as y=3x). That would translate to English as is a function of, which sounds fine:

Y is a function of X.

Perhaps a more English version would be "on the basis of" or something like that, or even, "They choose their holiday destination depending on the local weather."