Create a conditional function in script

Hello,

I'm trying to create a conditional equation in Matlab. I created a simple test script below and receive errors for "Missing or extra characters". In my test, I am trying to create a simple function "fun", where fun=2*R if R>0 and fun=3*R if R<=0.

close all
clear all
clc

syms R

fun(R)=
if R>0
    2*R
elseif R<=0
    3*R
end

It appears my approach is just incorrect. Any help is much appreciated.

Thanks!

Josh

[Matt J]

Does it have to be a symbolic function?