A library of coordinate system

A library of coordinate system math calculation.

坐标系数学计算方法库。

下载release的文件或者npm install --save mathjs-geo，支持以下任一方式加入前端项目中：

1、作为JS文件通过<script>引入html中：

<script src="./dist/mathjs-geo.min.js"></script>

2、支持ES6+的import引入：

import mathgeo from 'mathjs-geo';

3、支持CommonJS语法引入：

const mathgeo = require('mathjs-geo'); API Doc 方法文档 Math 数学方法

As we know, float number arithmetic is inaccurate. mathgeo provides four more accurate functions(add, subtract, multiply, and divide).

正如我们所知，浮点数运算是不精确的，mathgeo提供了加减乘除的4个方法，能让浮点数运算也能得到较为精确的结果。

add 加法

mathgeo.add(1.24, 567.0932); // 568.3332 mathgeo.add(0.312, 690.4, 78, 33.34); // 802.052

sub 减法

mathgeo.sub(1.24, 1); // 0.24 mathgeo.sub(87.4, 1.028, 99.09); // -12.718

multi 乘法

mathgeo.multi(3.4, 61.812, 2); // 420.3216

div 除法

mathgeo.div(5, 2, 3, 4.2); // 0.19841269841269843

In addition, round method can help you round the float number.

另外，还有四舍五入的方法，保留n位小数。

round 四舍五入

mathgeo.round(23.1119, 0); // 23 mathgeo.round(23.1119, 1); // 23.1 mathgeo.round(23.1119, 2); // 23.11 mathgeo.round(23.1119, 3); // 23.112 Geography 地理方法

At present, only 2d methods are supported, and 3d methods will be added in the future.

目前只支持2d的方法，未来将补充3d的方法。

The following methods are based on a two-dimensional coordinate system, where each point in space has coordinates (x, y) representing its position.

以下方法基于二维坐标系，即空间内每个点都有坐标(x�, y)表示其位置。

getKB([[x1, y1], [x2, y2]])

Calculate the k and b of the equation y=k*x+b. points [x1, y1] and [x2, y2] are on the line y=k*x+b.

求斜截式y=k*x+b的k与b。点[x1, y1]和点[x2, y2]在直线 y=k*x+b 上。

mathgeo.getKB([[0.5, 1.5], [2.5, 1]]); // {k: -0.25, b: 1.625} mathgeo.getKB([[0.5, 1.5], [2.5, 1.5]]); // {k: 0, b: 1.5} mathgeo.getKB([[0.5, 1.5], [0.5, 3]]); // null（直线与y轴平行，返回null）

getVertical([x, y], [[x1, y1], [x2, y2]], l)

Find the coordinates of both ends of the line segment whose length is l and is perpendicular to the straight line [[x1, y1], [x2, y2]]. The required line segment is divided equally by point [x,y].

求过点[x,y]并与直线垂直的长度为l的线段两端点坐标(所求线段被点[x,y]平分)。

mathgeo.getVertical([4, 2.125], [[6.5, 1.5], [0.5, 3]], 10); // [[2.787,-2.727],[5.213,6.977]]

getParallel([x, y], [[x1, y1], [x2, y2]], l)

Find the coordinates of both ends of the line segment whose length is l and is parallel to the straight line [[x1, y1], [x2, y2]]. The required line segment passes through the point [x,y] and is divided equally by point [x,y].

求过点[x,y]作与直线平行的长度为l的线段两端点坐标(所求线段被点[x,y]平分)。

mathgeo.getParallel([1, 1], [[6.5, 1.5], [0.5, 3]], 10); // [[-3.851,2.213],[5.851,-0.213]]

getExtension([x, y], [[x1, y1], [x2, y2]], l)

Find the coordinates of the points where the distance between [x, y] and the point is l ([x, y] and the required points are all on the line [[x1, y1], [x2, y2]]).

求直线[[x1, y1], [x2, y2]]上与点[x,y]的距离为l的点的坐标(点[x,y]也在直线上)。

mathgeo.getExtension([4, 2.125], [[6.5, 1.5], [0.5, 3]], 10); // [[-5.701,4.55],[13.701,-0.3]]

getAngle([[x1, y1], [x2, y2]])

Get the angle of the line [[x1, y1], [x2, y2]].

求直线[[x1, y1], [x2, y2]]的角度(从X轴正向逆时针旋转的角度)。

mathgeo.getAngle([[1, 1], [2, 2]]); // -135

getYFromX(x, [[x1, y1], [x2, y2]])

Knowing the coordinates of the two points on the line and the x coordinate of third point, find the y coordinate of the third point.

已知直线上两点和第三点的x坐标，求出第三点的y坐标。

getXFromY(y, [[x1, y1], [x2, y2]])

Knowing the coordinates of the two points on the line and the y coordinate of third point, find the x coordinate of the third point.

已知直线上两点和第三点的y坐标，求出第三点的x坐标。

mathgeo.getYFromX(4, [[6.5, 1.5], [0.5, 3]]); // 2.125 mathgeo.getXFromY(2.125, [[6.5, 1.5], [0.5, 3]]); // 4

lineCross([[x1, y1], [x2, y2]], [[x3, y3], [x4, y4]])

Determine whether the two line segments intersect (line1: [[x1, y1], [x2, y2]], line2: [[x3, y3], [x4, y4]]). If they intersect, return the coordinates of the intersection point. If they do not intersect, return false.

判断两线段是否相交(点1与点2组成线段1，点3与点4组成线段2)，相交返回交点坐标，不相交返回false。

mathgeo.lineCross([[0, 0], [6, 6]], [[6.5, 1.5], [0.5, 3]]); // [2.5, 2.5] mathgeo.lineCross([[0, 0], [1, 1]], [[6.5, 1.5], [0.5, 3]]); // false

getClosestPointIdx([x, y], pointGroup, minDist)

Find the index of the point in the pointGroup which is nearest to point[x,y], to meet the distance less than minDist�, and return -1 if none is not satisfied.

找出点集合pointGroup中距离点[x,y]最近的点下标，要满足距离小于minDist，如果没有满足的返回-1。

const pointGroup = [ [0, 1], [2.5, 6], [2.6, -9] ]; mathgeo.getClosestPointIdx([0, 0], pointGroup, 1.5); // 0 mathgeo.getClosestPointIdx([10, 1], pointGroup, 5); // -1

getClosetLineIdx([x, y], lineGroup, minDist)

Find the index of the line in the lineGroup which is nearest to point[x,y], to meet the distance less than minDist�, and return -1 if none is not satisfied.

找出线集合lineGroup中距离点[x,y]最近的线下标，要满足距离小于minDist，如果没有满足的返回-1。

const lineGroup = [ [[0, 1], [1, 2]], [[3.5, 6], [-12, 9]], [[2, 5], [9, -11.6]] ]; mathgeo.getClosetLineIdx([9, -8], lineGroup, 10); // 2 mathgeo.getClosetLineIdx([1000, -8], lineGroup, 10); // -1

pointOnLine([x, y], [[x1, y1], [x2, y2]], t)

Determine if the point is on line segment. t is the deviation value (default is 0.01). If the deviation range is less than t, the point is also considered to be on the line segment.

判断点是否在线段上。t为偏差值(默认为0.01)，如果偏差范围小于t，也认为在线段上。

const line = [[0.5, 6.77], [10.654, 4.5628]]; mathgeo.pointOnLine([4.3, 5.9], line, 0.01); // true mathgeo.pointOnLine([4.3, 5.1], line, 0.5); // true mathgeo.pointOnLine([4.3, 5.1], line, 0.05); // false

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To be continued...