RCHART TUTORIAL, Chapter 3

Copyright 2003, J4L Components (http://www.java4less.com)
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Axis configuration / parameters

• The label
• The ticks
• The scale's labels
• The grid
• Cero possition axis
• Closed axis
• Dates
• Second Y axis
  
• Look of the axis
  
• X axis on top

RChart supports 3 axis, a horizontal axis (X) at the bottom of the chart, and 2 vertical axis to the left (Y) and to the right (Y2) of the chart.

The label

Each Axis can have an associate label. The label of the following example is "Million $":

The properties of the label are:

• Text: text of the label.
• Font: font used to paint the label.
• Color: color of the label.
• Vertical: if true, the text will be painted vertically (rotated).

The following example paints a blue vertical label with "Serif" font:

The ticks

RChart supports 2 kind of ticks:

• small ticks: these are ticks between big ticks, they do not have any label.
• big ticks: these ticks are always displayed with a label.

There are 2 ways you can control the number and position of the ticks in the scale:

Manual: You can use the following parameters to define the spacing between ticks:

• TICK_INTERVALY: distance between small ticks (in axis units).
• BIG_TICK_INTERVALY: Number of small tick between big ticks. Note that these are not axis units, these are number of small ticks.

 

the default values are:

an example is:

Automatic: you can also let RChart calculate the value for the tick interval using the following parameters:

• YAXIS_AUTO_TICKS: if not 0 , Rchart will calculate the tick interval for the Y axis. This parameter is used to define the number of desired ticks.
  
• YAXIS_PREF_TICK_INTERVAL: Only used if AXIS_AUTO_TICKS is true. RChart will use the interval in this list which is more appropiate to get the desired amount of ticks. The default is:

VALUE="0.1|0.5|1|5|10|25|50|100|250|500|1000|5000|10000|50000|100000|500000|1000000"

For example, if your values range from 0 till 300 and the desired number of ticks is 10. RChart will select tick_interval=25 which will result in 12 ticks. See screenshot.

Other ticks parameters

If you don't want to have small ticks you can set BIG_TICK_INTERVALY=1. For example:

Ticks at irregular interval

The tick interval parameters allows you to define the position of the ticks. These are displayed at fixed intervals only. You can also use the BIG_TICK_INTERVAL_LISTY parameter to define the positions where the big ticks should appear. For example:

The following parameters allow you to control the length of the ticks. For example, you can remove the small ticks by making its length=0:

The scale labels

Labels are always displayed at the big ticks positions. The following parameters allow you to modify the labels.

XAXIS_LABEL_FORMAT. If XAXIS_INTEGER is false, this format will be used to draw the label. For example "#####.00" will always display 2 decimal digits. The format uses the following symbols:

• 0 a digit,
• # a digit, zero shows as absent
• . placeholder for decimal separator
• , placeholder for grouping separator.
• - default negative prefix.

The following parameter will remove the digits right of the decimal separator:

• You can specify your own text for the labels using:

You can split your labels in sereval lines by using "\n".

or paint labels vertically:

The grid

RChart will by default no display a grid:

however you can add the grid with the following parameters:

which let you define the style of the line used for the grid lines.

If you want to get a finer grid you can display the grid at the small tick positions with:

You can of course display lines for 1 axis only, for example:

Cero position axis

If you scale's minimum value is less than cero, you might want to paint a line at the cero possition to be used as reference by the user.

You can also define the cero axis to include the ticks (the labels are still painted at the bottom of the chart).

Closed axis

The following parameters allows you create a "frame" around the chart.

Dates

You can also use dates as labels for the ticks with the following parameters:

• XAXIS_DATE_FORMAT (default is dd-MMM-yyyy): format of the label. Use "MMM" to display only the month's name.
• XAXIS_DATE_STEP: date step for consecutive (small) ticks. The default is "d" which means 1 step/tick is 1 day. Other values are "m" (months), "w" (week) , "y" (year), "h" (hours) and "n" (minutes). You can also use "d3" ( 3 days), "m2" (2 months) ....
• XAXIS_INITIAL_DATE: this date will be used as base (first tick) if you want to calculate dates for the tick labels. Incompatible with logarithmic scales.
  

will result in the following secuence of ticks/labels

- big tick, label "01-Jan-01"
- small tick, no label
- big tick, label "03-Jan-01"
- small tick, no label
- big tick, label "05-Jan-01"
- .....

Example 1:

Example 2:

Example 3:

Second Y Axis

In order to activate the second Y axis you must use:

Y2AXIS =true

then you can define which data serie will use the scale of the second axis (serie 2 is the blue line)

Look of the axis

The following three parameters define the color and style of the axis

X Axis on top

If you want to place the x scale on the top of the chart, instead of on the bottom you can use the following parameters:

Note that this is not supported for 3D charts.