contour

Documentation

Overview

Package contour traces iso-lines and fills iso-bands of a function sampled on a rectangular grid, by marching squares with linear interpolation along cell edges.

A grid is Z[i*nx+j] at (X[j], Y[i]); X and Y must be monotonic. Saddle cells (opposite corners on the same side of the level) are resolved by the value at the cell centre, taken as the mean of the four corners. NaN corners make a cell contribute nothing.

Index

• func Band(g Grid, lo, hi float64) [][]Pt
• func Lines(g Grid, level float64) [][]Pt
• type Grid
• type Pt

Functions

func Band

func Band(g Grid, lo, hi float64) [][]Pt

Band returns the region where lo <= z <= hi as polygons, one per grid cell that the band touches, all wound counter-clockwise in (x, y). Filled together under the nonzero rule they make the band without seams.

func Lines

func Lines(g Grid, level float64) [][]Pt

Lines returns the iso-lines at level as polylines. Lines that close on themselves repeat their first point at the end.

Types

type Grid

type Grid struct {
	X, Y []float64 // len nx and ny
	Z    []float64 // ny*nx, row-major: Z[i*nx+j] is at (X[j], Y[i])
}

Grid is a function sampled on a rectangular grid.

type Pt

type Pt struct{ X, Y float64 }

Pt is a point in grid (data) coordinates.