DynamicCoordinates Command

DynamicCoordinates[ <Point A>, <Number X>, <Number Y> ]

Creates a point with coords (X, Y). This point is dependent, but can be moved. Whenever you try to move the new point to coordinates (x, y), point A is moved there and coordinates for the new point are calculated. Works best if point A is not visible and dragging is done with the mouse. At least one of X and Y should depend on A.

Example:

• Let A be a point and B = DynamicCoordinates[A, round(x(A)), round(y(A))]. When you try to move B to (1.3, 2.1) using the Move Tool, point A becomes (1.3, 2.1) and B appears at (1,2).
• B = DynamicCoordinates[A, x(A), min(y(A), sin(x(A)))] creates a point under sin(x).

Note: PointIn[y < sin(x)] is the easier solution in this case.

The following examples show other ways to restrain the positions of a point C:

• Let A = Point[xAxis] and B = Point[xAxis].

Now type in the Input Bar:

DynamicCoordinates[B, Min[x(B), x(A)], 0] and press Enter

SetVisibleInView[B, 1, false] and press Enter

SetLayer[C, 1] and press Enter

Now, C cannot be moved to the right of A.

• Define A=(1, 2).

Now, type in the Input Bar:

SetVisibleInView[A, 1, false] and press Enter

B = DynamicCoordinates[A, If[x(A) > 3, 3, If[x(A) < -3, -3, If[x(A) < 0, round(x(A)), x(A)]]], If[x(A) < 0, 0.5, If[y(A) > 2, 2, If[y(A) < 0, 0, y(A)]]]] and press Enter

• This example makes A a sticky point when a point C is dragged near it. Define A = (1, 2) and B = (2, 3).

Now, type in the Input Bar:

SetVisibleInView[B, 1, false] and press Enter

C = DynamicCoordinates[B, If[Distance[A, B] < 1, x(A), x(B)], If[Distance[A, B] < 1, y(A), y(B)]].