83 lines
2.2 KiB
Go
83 lines
2.2 KiB
Go
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package gofpdf
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// Adapted from Nice Numbers for Graph Labels by Paul Heckbert from "Graphics
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// Gems", Academic Press, 1990
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// Paul Heckbert 2 Dec 88
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// https://github.com/erich666/GraphicsGems
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// LICENSE
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// This code repository predates the concept of Open Source, and predates most
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// licenses along such lines. As such, the official license truly is:
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// EULA: The Graphics Gems code is copyright-protected. In other words, you
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// cannot claim the text of the code as your own and resell it. Using the code
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// is permitted in any program, product, or library, non-commercial or
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// commercial. Giving credit is not required, though is a nice gesture. The
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// code comes as-is, and if there are any flaws or problems with any Gems code,
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// nobody involved with Gems - authors, editors, publishers, or webmasters -
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// are to be held responsible. Basically, don't be a jerk, and remember that
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// anything free comes with no guarantee.
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import (
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"math"
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)
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// niceNum returns a "nice" number approximately equal to x. The number is
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// rounded if round is true, converted to its ceiling otherwise.
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func niceNum(val float64, round bool) float64 {
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var nf float64
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exp := int(math.Floor(math.Log10(val)))
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f := val / math.Pow10(exp)
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if round {
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switch {
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case f < 1.5:
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nf = 1
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case f < 3.0:
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nf = 2
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case f < 7.0:
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nf = 5
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default:
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nf = 10
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}
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} else {
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switch {
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case f <= 1:
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nf = 1
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case f <= 2.0:
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nf = 2
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case f <= 5.0:
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nf = 5
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default:
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nf = 10
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}
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}
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return nf * math.Pow10(exp)
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}
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// TickmarkPrecision returns an appropriate precision value for label
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// formatting.
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func TickmarkPrecision(div float64) int {
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return int(math.Max(-math.Floor(math.Log10(div)), 0))
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}
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// Tickmarks returns a slice of tickmarks appropriate for a chart axis and an
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// appropriate precision for formatting purposes. The values min and max will
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// be contained within the tickmark range.
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func Tickmarks(min, max float64) (list []float64, precision int) {
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if max > min {
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spread := niceNum(max-min, false)
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d := niceNum((spread / 4), true)
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graphMin := math.Floor(min/d) * d
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graphMax := math.Ceil(max/d) * d
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precision = TickmarkPrecision(d)
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for x := graphMin; x < graphMax+0.5*d; x += d {
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list = append(list, x)
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}
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}
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return
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}
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