Help with aggregate graph

I have a slide where students will be dragging a point to a position and sharing their point via a button. Aggregate shows all student points on the graph once the button is pressed. My issue is that prior to the button being pressed, there must be a value already assigned to the numberList because I have a mysterious y=x line showing up. Can someone help with this? Here is the activity. My Activity


Add a restriction for the length of one of your aggregate lists for the point in your graph. Like if your x-coordinate list is “X”:

(X,Y) {length(X)>0}

Edit: Actually, it looks like a2 and b2 are the issue. Put restrictions on those. They’re being treated as a y=x situation until your line of best fit (and thus a1 and b1) are defined.

Thanks @Daniel_Grubbs. That is interesting that they take on the y=x before (A,B) get populated.

It’s just a bivariate equation before there’s data (i.e. b2 and b1 are undefined variables), so it’s treated as such for graphing purposes. Just as you can create functions using any variable you see fit without being required to “convert” to x and y variables.