How can I express that if an expression evaluates to a negative number, I assign it a value of zero? Is it possible to do this without repeating the function twice?
Here is an example
$f(\vec{\phi})=\begin{cases} f(\vec{\phi}) & \text{for}\; f(\vec{\phi}) \gt 0 \\\ 0 & \text{for}\; f(\vec{\phi})\lt 0. \end{cases}$