scale/interface.go

// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package scale

// A Quantative scale is an invertible function from some continuous
// input domain to an output range of [0, 1].
type Quantitative interface {
	// Map maps from a value x in the input domain to [0, 1]. If x
	// is outside the input domain and clamping is enabled, x will
	// first be clamped to the input domain.
	Map(x float64) float64

	// Unmap is the inverse of Map. That is, if x is in the input
	// domain or clamping is disabled, x = Unmap(Map(x)). If
	// clamping is enabled and y is outside [0,1], the results are
	// undefined.
	Unmap(y float64) float64

	// SetClamp sets the clamping mode of this scale.
	SetClamp(bool)

	// Ticks returns major and minor ticks that satisfy the
	// constraints given by o. These ticks will have "nice" values
	// within the input domain. Both arrays are sorted in
	// ascending order and minor includes ticks in major.
	Ticks(o TickOptions) (major, minor []float64)

	// Nice expands the input domain of this scale to "nice"
	// values for covering the input domain satisfying the
	// constraints given by o. After calling Nice(o), the first
	// and last major ticks returned by Ticks(o) will equal the
	// lower and upper bounds of the input domain.
	Nice(o TickOptions)

	// A Quantitative scale is also a Ticker.
	Ticker
}

// A QQ maps from a source Quantitative scale to a destination
// Quantitative scale.
type QQ struct {
	Src, Dest Quantitative
}

// Map maps from a value x in the source scale's input domain to a
// value y in the destination scale's input domain.
func (q QQ) Map(x float64) float64 {
	return q.Dest.Unmap(q.Src.Map(x))
}

// Unmap maps from a value y in the destination scale's input domain to
// a value x in the source scale's input domain.
func (q QQ) Unmap(x float64) float64 {
	return q.Src.Unmap(q.Dest.Map(x))
}