After Effects Grid maker

I was messing about with expressions in After Effects a while ago and this week I saw two people online talking about something similar to this, so I thought I'd post the expressions here...

Basically, you start with one layer in a comp, then add these expressions to position and to scale. Then when you duplicate that layer, say 9 times, you get a grid of 3 x 3 to fit your comp size. Then you'd just replace the footage in each layer as needed.

Position expression;

NumberAcross = Math.ceil(Math.sqrt(thisComp.numLayers));

W = thisComp.width/NumberAcross;

H = thisComp.height/NumberAcross;

gridPos = index ;

col = gridPos % (NumberAcross+0.0001) ;

row = Math.ceil(1/(NumberAcross/gridPos));

xPos = (thisComp.width/NumberAcross)*(col-1);

yPos = (thisComp.height/NumberAcross)*(row-1);

[(xPos+W/2) ,(yPos+H/2)]

Scale expression;

NumberAcross = Math.ceil(Math.sqrt(thisComp.numLayers));