Subversion-Projekte lars-tiefland.cienc

Title: Options Tutorial

This document will help you understand how jqPlot's options
relate to the API documentation and the jqPlot object
itself.  For a listing of options available to jqPlot,
see <jqPlot Options> in the jqPlotOptions.txt file.

The key to effectively using jqPlot is understanding jqPlot's
options.  The online documentation is API documentation.  While
it explains what attributes and methods various objects possess,
it doesn't explain how to use or set those attributes through 
options.  This tutorial will help explain that.

Let's assume you are creating a plot 
like this:

> chart = $.jqplot('chart', dataSeries, optionsObj);

First, note that you shouldn't try to directly set attributes on the
"chart" object (like chart.grid.shadow) after your call to $.jqplot().  
At best this won't do anything **(see below). You should pass options in via
the "optionsObj".

The optionsObj really represents the plot object (jqPlot object, not
to be confused with the $.jqplot function which will create a jqPlot
object).  Attributes you specify on that object will be merged with
attributes in the jqPlot object.  The axes, legend, series, etc. are
attributes on the jqPlot object.  The jqPlot/optionsObj object looks
something like (only some attributes shown):

> jqPlot-|
>        |-seriesColors
>        |-textColor
>        |-fontFamily
>        |-fontSize
>        |-stackSeries
>        |-series(Array)-|
>        |               |-Series1-|
>        |               |         |-lineWidth
>        |               |         |-linePattern
>        |               |         |-shadow
>        |               |         |-showLine
>        |               |         |-showMarker
>        |               |         |-color
>        |               |-Series2...
>        |               |-...
>        |               |-SeriesN
>        |
>        |-grid(Object)-|
>        |              |-drawGridLines
>        |              |-background
>        |              |-borderColor
>        |              |-borderWidth
>        |              |-shadow
>        |
>        |-title(Object)-|
>        |               |-text
>        |               |-show
>        |               |-fontFamily
>        |               |-fontSize
>        |               |-textAlign
>        |               |-textColor
>        |
>        |-axes(Object)-|
>        |              |-xais-|
>        |              |      |-min
>        |              |      |-max
>        |              |      |-numberTicks
>        |              |      |-showTicks
>        |              |      |-showTickMarks
>        |              |      |-pad
>        |
>        | ... and so on
 
The optionsObj should follow the same construction as if it were a
jqPlot object (with some exceptions/shortcuts I'll mention in a
moment).  So generally, when you see something like
"this.drawGridLines" in the grid properties in the docs, just replace
"this" with "grid" in your options object.  So it becomes
optionsObj.grid.drawGridLines.  Do likewise with the other objects in
the plot, replacing "this", with the respective attribute on the plot
like "legend" or "title".  Series and Axes are handled a little
differently, because series is an array and axes has 4 distinct children
"xaxis", "yaxis", "x2axis" and "y2axis".

So, to remove the shadow from the grid and change the grid border size
you would do:

> optionObj = {grid:{shadow:false, borderWidth:9.0}};

To do the same as above but also make all the text in the plot red you
would do:

> optionObj = {
>    textColor:"#ff0000",
>    grid:{shadow:false, borderWidth:9.0}
> }

Here is a more deeply nested example. Say you want to specify a min
and max on your y axis and use a specific color for your second
series.  That would look like:

> optionsObj = {
>    axes:{yaxis:{min:5, max:230}},
>    series:[{},{color:"#33ff66"}]
> }

Note that series options are an array in order of the series data you
sent in to your plot.  To get to the second series, you have to put an
object (even if empty) in place of the first series.

There is a handy shortcut to assign options to all axes or all series
at one go.  Use axesDefaults and seriesDefaults.  So, if you wanted
both x and y axes to start at 0 and you wanted all series to not show
markers, you could do:

> optionsObj = {axesDefaults:{min:0}, seriesDefaults:{showMarker:false}}

Another shortcut is for the plot title.  Normally, you would assign
options to the title as an object.  If you specify a title option as a
string, it will assign that to the title.text property automatically.
So these two are equivalent:

> optionsObj = {title:{text:"My Plot"}}

and

> optionsObj = {title:"My Plot"}

Where things need more explanation is with renderers, plugins and
their options.  Briefly, what's the difference between a renderer and
a plugin.

A renderer is an object that is used to draw something and gets
attached to an existing object in the plot in order to draw it.  A
plugin does more than just provide drawing functionality to an
object; it can calculate a trend line, change the
cursor, provide event driven functionality, etc.  I consider renderers
plugins, but plugins don't have to be renderers.

So, how do you use renderers and plugins, and specify their options?
Some common renderers are for bar charts and category axes.  If you
want to render your series as a bar chart with each set of bars
showing up in a category on the x axis, you do:

> optionsObj = {
>    seriesDefaults:{renderer:$.jqplot.BarRenderer},
>    axes:{xaxis:{renderer:$.jqplot.CategoryAxisRenderer}}
> }

This replaces the default renderer used for all series in the plot
with a bar renderer and the x axis default renderer (but not any other
axis) with a category renderer.

Now, how would I assign options to those renderers?  The renderer's
attributes may not be present in the pre-existing jqPlot object, they
may be specific to the renderer.  This is done through the
"rendererOptions" option on the appropriate object. So, if I wanted my
bars to be 25 pixels wide, I would do:


> optionsObj = {
>    seriesDefaults:{
>        renderer:$.jqplot.BarRenderer},
>        rendererOptions:{
>            barWidth:25
>        },
>    axes:{xaxis:{renderer:$.jqplot.CategoryAxisRenderer}}
> }

Again, this is using the "seriesDefaults" option, which will apply
options to all series in the plot.  You could do the same on any
particular series in the plot through the "series" options array.

Plugins are free to add their own options.  For example, the
highlighter plugin has its own set of options that are unique to it.
As a result, it responds to options placed in the "highlighter"
attribute of your options object.  So, if I wanted to change the
highlighter tooltip to fade in and out slowly and be positioned
directly above the point I'm highlighting:

> optionsObj = {
>     highlighter:{tooltipFadeSpeed:'slow', tooltipLocation:'n'}
> }

Other plugins, like dragable and trendlines, add their options in with
the series.   (Yes, that's the correct name for the dragable plugin; it
doesn't use the correct spelling of "draggable".)
This is because both of those plugins can have different
options for different series in the plot.  So, if you wanted to specify the
color for the dragable plugin and constrain it to drag only on the x axis as well
as specify the color of the trend line you could do:

> series:[{
>     dragable: {
>         color: '#ff3366',
>         constrainTo: 'x'
>     },
>     trendline: {
>         color: '#cccccc'
>     }
> }]

This would apply those options to the first series only.  If you had 2 series
and wanted to turn off dragging and trend lines on the second series, you could do:

> series:[{
>     dragable: {
>         color: '#ff3366',
>         constrainTo: 'x'
>     },
>     trendline: {
>         color: '#cccccc'
>     }
> }, {
>    isDragable: false,
>    trendline:{
>        show: false
>    }
> }]

Note, series draggability is turned off with the "isDragable" option directly on 
the series itself, not with a suboption of "dragable".  This may be improved 
in the future.

I hope this is helpful. 
A few key points to remember:

- When you see "this" in the api docs, you generally replace it with
the name of the object (in lowercase) you are looking at in your
options object.
- seriesDefaults and axesDefaults are convenient shortcuts.
- to assign options to a renderer, generally use the "rendererOptions"
- plugins may add their own options attribute, like "highlighter" or
"cursor".

** Note:  you can set attributes after the plot is created (like
plot.grid.shadow = false), but you'll have to issue the appropriate
calls to possibly reinitialize and redraw the plot.  jqPlot can
definitely handle this to change the plot after creation (this is how
the dragable plugin updates the plot data and the trend line plugin
recomputes itself when data changes).  This hasn't been documented
yet, however.