How does one represent this in math

[wildman]

How does one represent this in math...

Homework Statement

How does one represent the following in mathematical notation:

if(x >= a) then y = x-a
else x=0

Homework Equations

The Attempt at a Solution

Just y= x-a will not do it because it becomes negative when x is less than a and that is not what I want...

 

[tiny-tim]

How does one represent the following in mathematical notation:

if(x >= a) then y = x-a
else x=0

Hi wildman!

How about using min or max (or is it inf or sup )?

 

[HallsofIvy]

I'm not sure what you kind of notation you want. I would write that as either
$$y= \left(\begin{array}{c} x- a if x\ge a \\ 0 if x> a\end{array}\right$$

Or as y= H(x-a)(x-a) where H(x) is the Heaviside step function.