# Difference between revisions of "Point"

A WASSERMANN (talk | contribs) |
A WASSERMANN (talk | contribs) |
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</source> | </source> | ||

− | The size can be controlled | + | The size of the points can be controlled independently. |

<jsxgraph box="jxgbox3b" width="600px" height="200px"> | <jsxgraph box="jxgbox3b" width="600px" height="200px"> | ||

var b3b = JXG.JSXGraph.initBoard('jxgbox3b', {originX: 40, originY: 100, unitX: 40, unitY: 40}); | var b3b = JXG.JSXGraph.initBoard('jxgbox3b', {originX: 40, originY: 100, unitX: 40, unitY: 40}); | ||

Line 117: | Line 117: | ||

b3b.create('point',[10,0], {face:'o'}, size:32); | b3b.create('point',[10,0], {face:'o'}, size:32); | ||

</jsxgraph> | </jsxgraph> | ||

+ | |||

+ | <source lang="javascript"> | ||

+ | var b3b = JXG.JSXGraph.initBoard('jxgbox3b', {originX: 40, originY: 100, unitX: 40, unitY: 40}); | ||

+ | b3b.create('point',[1,0], {face:'o'}, size:1); | ||

+ | b3b.create('point',[2,0], {face:'o'}, size:2); | ||

+ | b3b.create('point',[3,0], {face:'o'}, size:4); | ||

+ | b3b.create('point',[5,0], {face:'o'}, size:8); | ||

+ | b3b.create('point',[7,0], {face:'o'}, size:16); | ||

+ | b3b.create('point',[10,0], {face:'o'}, size:32); | ||

+ | </source> | ||

=== Fixed points=== | === Fixed points=== |

## Revision as of 13:19, 12 March 2010

## Contents

## Construction of a free point

This example shows how to construct a simple, draggable point. It is produced by the following commands:

```
<div id="jxgbox" class="jxgbox" style="width:500px; height:200px;"></div>
<script type="text/javascript">
var board = JXG.JSXGraph.initBoard('jxgbox', {originX: 200, originY: 100, unitX: 50, unitY: 50});
var p = board.createElement('point',[1,1]);
</script>
```

The JavaScript code has to be placed AFTER the div element which will contain the construction. From now on, we will only show the JavaScript code.

## Attributes of a point

### User defined name

Several attributes can be given to change the properties of a point, for example a name.

```
var b2 = JXG.JSXGraph.initBoard('jxgbox2', {originX: 200, originY: 100, unitX: 50, unitY: 50});
var p = b2.createElement('point',[1,1], {name:'X',style:5});
```

This point will be labeled with "X":

### Point styles

The property type of a point can attain the values 0..12. Alternatively you can use these equivalent constants for that:

Constant | Value | Short description |
---|---|---|

JXG.POINT_STYLE_X_SMALL | 0 | Small x |

JXG.POINT_STYLE_X | 1 | Medium x |

JXG.POINT_STYLE_X_BIG | 2 | Big x |

JXG.POINT_STYLE_CIRCLE_TINY | 3 | Tiny circle |

JXG.POINT_STYLE_CIRCLE_SMALL | 4 | Small circle |

JXG.POINT_STYLE_CIRCLE | 5 | Medium circle |

JXG.POINT_STYLE_CIRCLE_BIG | 6 | Big circle |

JXG.POINT_STYLE_SQUARE_SMALL | 7 | Small square |

JXG.POINT_STYLE_SQUARE | 8 | Medium square |

JXG.POINT_STYLE_SQUARE_BIG | 9 | Big square |

JXG.POINT_STYLE_PLUS_SMALL | 10 | Small + |

JXG.POINT_STYLE_PLUS | 11 | Medium + |

JXG.POINT_STYLE_PLUS_BIG | 12 | Big + |

In this examples we use a for loop to create 13 points.

```
var b3 = JXG.JSXGraph.initBoard('jxgbox3', {originX: 40, originY: 100, unitX: 40, unitY: 40});
for (var i=0;i<13;i++) {
var p = b3.create('point',[i,0], {name:'P_{'+i+'}', style:i});
}
p.setProperty({fixed:true});
```

### Point faces

Meanwhile point style is superseded by the attributes *face* and *size*, which allow a better control of the display of points.

```
var b3a = JXG.JSXGraph.initBoard('jxgbox3a', {originX: 40, originY: 100, unitX: 40, unitY: 40});
b3a.create('point',[1,0], {face:'o'}); // or circle
b3a.create('point',[2,0], {face:'[]'}); // or square
b3a.create('point',[3,0], {face:'x'}); // or cross
b3a.create('point',[4,0], {face:'+'}); // or plus
b3a.create('point',[5,0], {face:'A'}); // or triangleUp
b3a.create('point',[6,0], {face:'v'}); // or triangleDown
b3a.create('point',[7,0], {face:'>'}); // or triangleLeft
b3a.create('point',[8,0], {face:'<'}); // or triangleRight
b3a.create('point',[9,0], {face:'<>'}); // or diamond
```

The size of the points can be controlled independently.

```
var b3b = JXG.JSXGraph.initBoard('jxgbox3b', {originX: 40, originY: 100, unitX: 40, unitY: 40});
b3b.create('point',[1,0], {face:'o'}, size:1);
b3b.create('point',[2,0], {face:'o'}, size:2);
b3b.create('point',[3,0], {face:'o'}, size:4);
b3b.create('point',[5,0], {face:'o'}, size:8);
b3b.create('point',[7,0], {face:'o'}, size:16);
b3b.create('point',[10,0], {face:'o'}, size:32);
```

### Fixed points

A property of an element may also be set after creating it. In the above example we set the property fixed of the last point, P_12, to true. I.e. the point is no longer draggable.

```
p.setProperty({fixed:true});
```

### Dependent points

A point can depend on any other geometric object. This dependence can be given by using JavaScript functions or terms in GEONExT syntax for coordinates.

#### GEONExT syntax

Here is an example using GEONExT syntax. The point A is draggable. The point B depends on point A: Its y-coordinate is set to 1 and its x-coordinate is set to the x-coordinate of A.

```
var b = JXG.JSXGraph.initBoard('jxgbox', {originX: 40, originY: 100, unitX: 40, unitY: 40});
var free = b.createElement('point',[0,0], {name:'A', style:5});
var dep = b.createElement('point',["X(A)",1], {name:'B', style:8});
```

#### JavaScript syntax

Now we do exactly the same with JavaScript syntax.

```
var b = JXG.JSXGraph.initBoard('jxgbox', {originX: 40, originY: 100, unitX: 40, unitY: 40});
var free = b.createElement('point',[0,0], {name:'A', style:5});
var dep = b.createElement('point',[function(){ return free.X();}, 1], {name:'B', style:8});
```

```
var free = b.createElement('point',[0,0], {name:'A', style:5});
```

Then we construct the dependent point "dep".

```
var dep = b.createElement('point',[function(){ return free.X();}, 1], {name:'B', style:8});
```

The first coordinate of "dep" is given as an anonymous function:

```
function(){ return free.X();}
```

This function returns the x-coordinate of the point "free".