Attached is a document with a function P(a) which contains several "if" sections, i.e. a different function applies depending on which value the dummy variables take. Can anyone help me by rewriting this is as a straight, closed-form (sigma operators are fine) function in a? Or explaining why in this particular case it is impossible, if it is? I'd like something I can use to compute values of P(a) from a. In the current form, it cannot be used to compute values directly as far as I know. My instinct is that you'd just need to separate out the operators for each different section. But really I have no idea. If you could help that would be great.