d3.deviation(array[, accessor]) Returns the standard deviation, defined as the square root of the bias-corrected variance, of the given array of numbers. If the array has fewer than two values, returns undefined. An optional accessor function may be specified, which is equivalent to calling array.map(accessor) before computing the standard deviation. This method ignores undefined and NaN values; this is useful for ignoring missing data.

d3.descending(a, b) Returns -1 if a is greater than b, or 1 if a is less than b, or 0. This is the comparator function for reverse natural order, and can be used in conjunction with the built-in array sort method to arrange elements in descending order. It is implemented as: function descending(a, b) { return b < a ? -1 : b > a ? 1 : b >= a ? 0 : NaN; } Note that if no comparator function is specified to the built-in sort method, the default order is lexicographic (alphabetical), n

d3.customEvent(event, listener[, that[, arguments]]) Invokes the specified listener, using the specified that this context and passing the specified arguments, if any. During the invocation, d3.event is set to the specified event; after the listener returns (or throws an error), d3.event is restored to its previous value. In addition, sets event.sourceEvent to the prior value of d3.event, allowing custom events to retain a reference to the originating native event. Returns the value returned

d3.curveStepBefore(context) Produces a piecewise constant function (a step function) consisting of alternating horizontal and vertical lines. The y-value changes before the x-value.

d3.curveStepAfter(context) Produces a piecewise constant function (a step function) consisting of alternating horizontal and vertical lines. The y-value changes after the x-value.

d3.curveStep(context) Produces a piecewise constant function (a step function) consisting of alternating horizontal and vertical lines. The y-value changes at the midpoint of each pair of adjacent x-values.

d3.curveNatural(context) Produces a natural cubic spline with the second derivative of the spline set to zero at the endpoints.

d3.curveMonotoneY(context) Produces a cubic spline that preserves monotonicity in x, assuming monotonicity in y, as proposed by Steffen in A simple method for monotonic interpolation in one dimension: “a smooth curve with continuous first-order derivatives that passes through any given set of data points without spurious oscillations. Local extrema can occur only at grid points where they are given by the data, but not in between two adjacent grid points.”

d3.curveMonotoneX(context) Produces a cubic spline that preserves monotonicity in y, assuming monotonicity in x, as proposed by Steffen in A simple method for monotonic interpolation in one dimension: “a smooth curve with continuous first-order derivatives that passes through any given set of data points without spurious oscillations. Local extrema can occur only at grid points where they are given by the data, but not in between two adjacent grid points.”

d3.curveLinearClosed(context) Produces a closed polyline through the specified points by repeating the first point when the line segment ends.