Measurement

Element

Display measurements of geometric elements and the arithmetic operations of measurements. Under the hood this is a text element which has a method Value. The text to be displayed is the result of the evaluation of a prefix expression, see JXG.PrefixParser.

The purpose of this element is to display values of measurements of geometric objects, like the radius of a circle, as well as expressions consisting of measurements.

Usage (signatures)
board.create('measurement', [x, y, expression]);

Here, expression is a prefix expression, see JXG.PrefixParser.

Parameters
Name Type Description
x PointLike
y PointLike
expression Array
Examples
var p1 = board.create('point', [1, 1]);
var p2 = board.create('point', [1, 3]);
var ci1 = board.create('circle', [p1, p2]);

var m1 = board.create('measurement', [1, -2, ['Area', ci1]], {
    visible: true,
    prefix: 'area: ',
    baseUnit: 'cm'
});

var m2 = board.create('measurement', [1, -4, ['Radius', ci1]], {
    prefix: 'radius: ',
    baseUnit: 'cm'
});


var p1 = board.create('point', [1, 1]);
var p2 = board.create('point', [1, 3]);
var ci1 = board.create('circle', [p1, p2]);
var seg = board.create('segment', [[-2,-3], [-2, 3]], { firstArrow: true, lastArrow: true});
var sli = board.create('slider', [[-4, 4], [-1.5, 4], [-10, 1, 10]], {name:'a'});

var m1 = board.create('measurement', [-6, -2, ['Radius', ci1]], {
    prefix: 'm1: ',
    baseUnit: 'cm'
});

var m2 = board.create('measurement', [-6, -4, ['L', seg]], {
    prefix: 'm2: ',
    baseUnit: 'cm'
});

var m3 = board.create('measurement', [-6, -6, ['V', sli]], {
    prefix: 'm3: ',
    baseUnit: 'cm',
    dim: 1
});

var m4 = board.create('measurement', [2, -6,
        ['+', ['V', m1], ['V', m2], ['V', m3]]
    ], {
    prefix: 'm4: ',
    baseUnit: 'cm'
});
Attributes

Own

baseUnit

dim

formatCoords

formatDirection

prefix

showPrefix

showSuffix

suffix

units

baseUnit

Description

This specifies the unit of measurement in dimension 1 (e.g. length). A power is automatically added to the string. If you want to use different units for each dimension, see Measurement#units.

Type
String
Default Value
''
See
Example
var p1 = board.create("point", [0,1]),
    p2 = board.create("point", [3,1]),
    c = board.create("circle", [p1, p2]);

board.create("measurement", [-2, -3, ["Perimeter", c]], {
    baseUnit: " m"
});
board.create("measurement", [1, -3, ["Area", c]], {
    baseUnit: " m"
});
Source
options.js, line 7476

dim

Description

Dimension of the measured data. This measurement can only be combined with a measurement of a suitable dimension. Overwrites the dimension returned by the Dimension() method. Normally, the default value null is used here to automatically determine the dimension.

However, if the coordinates or a direction vector are measured, the value is usually returned as an array. To tell the measurement that the function Measurement#formatCoords or Measurement#formatDirection should be used to display the array properly, 'coords' or 'direction' must be specified here.

Type
Number | 'coords' | 'direction'
Default Value
null
See
Source
options.js, line 7625

formatCoords

Description

Function to format coordinates. Does only have an effect, if Measurement#dim is set to 'coords'.

Type
function
See
Example
var p = board.create("point", [-2, 0]);

board.create("measurement", [0, -3, ["Coords", p]], {
    dim: 'coords',
    formatCoords: function (_,x,y,z) {
        if (parseFloat(z) !== 1)
            return 'Infinit coords';
        else
            return '(' + x + ' | ' + y + ')';
    }
});
Source
options.js, line 7643

formatDirection

Description

Function to format direction vector. Does only have an effect, if Measurement#dim is set to 'direction'.

Type
function
Example
var p1 = board.create("point", [0,1]),
    p2 = board.create("point", [3,1]),
    s = board.create("segment", [p1, p2]);

board.create("measurement", [0, -2, ["Direction", s]], {
    dim: 'direction',
    formatDirection: function (self,x,y) {
       return '\\[\\frac{' + y + '}{' + x + '} = ' +
           (!isFinite(y/x) ? '\\infty' : JXG.toFixed(y/x, self.visProp.digits)) +
           '\\]';
    },
    useMathJax: true
});
Source
options.js, line 7695

prefix

Description

String that is displayed before the measurement and its unit.

Type
String
Default Value
''
See
Source
options.js, line 7603

showPrefix

Description

Determines whether a prefix is displayed before the measurement value and unit.

Type
Boolean
Default Value
true
See
Source
options.js, line 7581

showSuffix

Description

Determines whether a suffix is displayed after the measurement value and unit.

Type
Boolean
Default Value
true
See
Source
options.js, line 7592

suffix

Description

String that is displayed after the measurement and its unit.

Type
String
Default Value
''
See
Source
options.js, line 7614

units

Description

This attribute expects an object that has the dimension numbers as keys (as integer or in the form of 'dimxx') and assigns a string to each dimension. If a dimension has no specification, Measurement#baseUnit is used.

Type
Object
Default Value
{}
See
Example
var p1 = board.create("point", [0,1]),
    p2 = board.create("point", [3,1]),
    c = board.create("circle", [p1, p2]);

board.create("measurement", [-3, -3, ["Perimeter", c]], {
    baseUnit: " m",
    units: {
         1: " length unit",
      2: " area unit"
    },
});
board.create("measurement", [1, -3, ["Area", c]], {
    baseUnit: " m",
    units: {
         dim1: " length unit",
      dim2: " area unit"
    },
});
Source
options.js, line 7521

Inherited

none

Throws

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

Type
Exception

Details

Type
JXG.Text
Source
element/measure.js, line 201