Why is the pow function returning NAN?

Question

When using the following function, I sometimes get NAN returned for some inputs; I think I'm getting NAN when I'm using negative values for the variables. How can I fix this?

pow(($LY/$FY),(1/10)) - 1

Answer 1

Add a check beforehand to ensure that $LY/$FY is positive. Alternatively, depending on what you're using it for, use the abs() function on that fraction to change negative numbers to positive ones.