How can I write functions for this m file

I can't write functions to solution this

   Xi+|yi|-z^2.    X>z>y
F= Zi.             Z>x
   Yi.             Y>x>z
   X^2+y^2.        X=z or y=z
Where i= 1,2,3....n

[Rik]

Have a read here (or here for more general advice) and here. It will greatly improve your chances of getting an answer.

[Steven Lord]

It's not clear what you want this function to accept as input nor what you want it to return as output. If you tell us that information, show us what you've already tried, and explain how it "misbehaves" we may be able to offer some guidance.

When I say explain how it "misbehaves", I mean please show the full red text of the error message, the full orange text of the warning message, or describe how what it returns differs from what you expected.

[dpb]

OK, I can see it's intended as a piecewise functional but there's some issues with lower and upper case instances of same letter variable and what the functional as function of i is to use for data source. Are these a known lookup table, for example, or some other functional or what???

[ANKUR KUMAR]

Come up with some trail code. Then we can able to help you.