transition.ease()

transition.ease([value])

Specifies the transition easing function for all selected elements. The value must be specified as a function. The easing function is invoked for each frame of the animation, being passed the normalized time t in the range [0, 1]; it must then return the eased time tʹ which is typically also in the range [0, 1]. A good easing function should return 0 if t = 0 and 1 if t = 1. If an easing function is not specified, it defaults to d3.easeCubic.

If a value is not specified, returns the current easing function for the first (non-null) element in the transition. This is generally useful only if you know that the transition contains exactly one element.