Andrew,
When code gets pasted into this forum, the minus signs can get converted to some other character, which breaks the expression. Try this version:
// Penner easeInOutExpo
function easeInOut (t,b,c,d) {
if (t <= 0) return b;
if (t >= d) return b + c;
if ((t/=d/2) < 1) return c/2*t*t*t*t*t + b;
return c/2*((t-=2)*t*t*t*t + 2) + b;
}
var xstartVal = 500;
var ystartVal = 500;
var xendVal = 500;
var yendVal = 800;
var startDur = 0;
var endDur = 1.8;
t = time - (startDur + inPoint);
d = endDur - startDur;
y = easeInOut (t,ystartVal, yendVal - ystartVal, d);
x = easeInOut (t,xstartVal, xendVal - xstartVal, d);
[x,y];
If you want a different ease, just change the code in the function (and the two references to the function if you change the name of the function).