How to parent rotation property to change position of another shape layer?

[Johannes5C22]

Hi, I'm trying to make an animation with one shape layer that rotates, and another layer that moves with the rotation, but horizontally. Is there any way to parent the rotation property to the other shape layers horizontal position? To explain the attached photo: I want the lines under the round shape to move when I rotate the round shape, like a scroll effect horizontally. 
Thanks!
/Jo 

[Mylenium]

A simple linear() expression will do with this pattern:

linear(refValue, refStart, refEnd, start, end)

All that's required is to fill in the links to the properties and set the values.

Mylenium 

[Johannes5C22]

Thank you so much! When you say "fill in the links", what do you mean? I'm a total beginner when it comes to expressions, should have written that in the post, sorry! 

[Dan Ebberts]

If you wanted Layer 1's rotation from -90 to +90 to correspond to a horizontal movement of 0 to 100 for Layer 2, you could use a position expression like this:

r = thisComp.layer("Layer 1").transform.rotation;
rMin= -90;
rMax = 90;
xMin = 0;
xMax = 100;
x = linear(r,rMin,rMax,xMin,xMax);
value + [x,0]

[Rick Gerard · Accepted solution]

I would use the diameter of the wheel to calculate the circumference (C = π D) and use that to move the layer in x. This expression would do that and also compensate for any scale changes in the Wheel layer.

src=thisComp.layer("Wheel");
d = src.sourceRectAtTime().width;
r = src.rotation / 360;
s = src.scale[0] * .01;
c = d * s;
x = Math.PI * c * r;
value + [x, 0];

 

[Johannes5C22]

Wow, thank you so much! Is there any way to make the lines move the opposite way?

[Johannes5C22]

Never mind, I figured it out! Thank you, all of you, for the help! 

[Johannes5C22]

One more question though, haha. Is there any way to do the same thing but for the wheel rotation to parent the number on an animated number count (text layer)? Let's say I wanted the number to start with "1860" and then be able to count upwards to ""2024". 
I apologize if I'm pushing it haha.