Slopefield

Element

A slope field is a graphical representation of the solutions to a first-order differential equation of a scalar function.

Plot a slope field given by a function f(x, y) returning a number.

Usage (signatures)
board.create('slopefield', [F, xData, yData]);
Parameters
Name Type Description
F function | String

Function f(x, y) returning a number.
xData Array

Array of length 3 containing start value for x, number of steps, end value of x. The vector field will contain (number of steps) + 1 vectors in direction of x.
yData Array

Array of length 3 containing start value for y, number of steps, end value of y. The vector field will contain (number of steps) + 1 vectors in direction of y.
Examples
var field = board.create('slopefield', [
    (x, y) => x * x - x - 2,
    [-6, 25, 6], // Horizontal mesh
    [-5, 20, 5]  // Vertical mesh
]);


// Slider to control length of vectors
var s = board.create('slider', [[-3, 7], [3, 7], [0, 0.33, 1]], {name: 'length'});
// Slider to control number of steps
var stepsize = board.create('slider', [[-3, 6], [3, 6], [1, 20, 100]], {name: 'steps', snapWidth: 1});

var field = board.create('slopefield', [
    (x, y) => x * x - y * y,
    [-6, () => stepsize.Value(), 6],
    [-5, () => stepsize.Value(), 5]],
    {
        strokeWidth: 1.5,
        highlightStrokeWidth: 0.5,
        highlightStrokeColor: JXG.palette.blue,

        scale: () => s.Value(),

        arrowHead: {
            enabled: false,
            size: 8,
            angle: Math.PI / 16
        }
    });
Attributes

Own

arrowhead

scale

arrowhead

Description

Customize arrow heads of vectors. Be careful! If enabled this will slow down the performance. Fields are:

  • enabled: Boolean
  • size: length of the arrow head legs (in pixel)
  • angle: angle of the arrow head legs In radians.
Type
Object
Default Value
{enabled: false, size: 5, angle: Math.PI * 0.125}
Source
options.js, line 9262

scale

Description

Set length of the vectors in user coordinates. This in contrast to vector fields, where this attribute just scales the vector.

Type
Number | function
Default Value
1
See
Source
options.js, line 9251

Inherited

none

Methods

Own

setF

setF(func) → {Object}

Set the defining functions of slope field.

Example

field.setF((x, y) => x * x + y * y);
board.update();

Parameters

Name Type Description
func function

Function f(x, y) returning a number.

Returns

Reference to the slope field object.

Type
Object

Details

Source
element/vectorfield.js, line 397

Inherited

none

Throws

If the element cannot be constructed with the given parent objects an exception is thrown.

Type
Error

Details

Type
JXG.Curve
Source
element/vectorfield.js, line 268