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RCHART TUTORIAL, Chapter 4

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

Maximum and minimum values
Logarithmic Scales

Maximum and minimum values

The following section describes how the maximum and minimum values of the scale are calculated. The examples refer to the Y-Axis, however the same parameters are also available for the X and Y2 axis.

If you want to plot the following values:

10, 41 , 48 , 39, 36 ,34 , 49

you can use the following way in order to calculate the maximum and minimum values of the axis:

default maximum and minimum. If you do not specify the minimum and/or maximum value for the scale, rchart will use the minimum and maximum value of the set you want to chart. The result will be: minimum=10 and maximum=49

specify maximum and minimum. You can also calculate the values and pass them to rchart. For example you can use

*Parameters*	*Description*	*Equivalent Java[TM] class/property*
YSCALE_MIN=0 YSCALE_MAX=50	Minimum value of the scale Maxumim value of the scale	xaxis.scale.min yaxis.scale.max

the result will be:

preferred maximum and minimum. You can also let RChart calculate the values from a list of predefined values. In this case you must use the following parameters:

*Parameters*	*Description*	*Equivalent Java[TM] class/property*
YSCALE_EXACT_MAX=true YSCALE_EXACT_MIN=true YSCALE_PREF_MAXMIN=-1000000\|-500000\|-100000\|-50000\|-10000\|-5000\|-1000\|-500\|-250\|-100\|-50\|-25-10\|-5\|-1\|-0.5\|-\|0.1\|0\|0.1\|0.5\|1\|5\|10\|25\|50\|100\|250\|500\|1000\|5000\|10000\|50000\|100000\|500000\|1000000	Take the min. and max. values from the list of preferred values.	yaxis.scale.exactMaxValue yaxis.scale.exactMinValue yaxis.scale.preferred_MaxMin_values

RChart will use one of the values from the list you provided. This list must be sorted in ascending order and RChart will always select the first value that meets the condition:

for the minimum: will select the highest value that is smaller than all values in your data set. (See red value in list)
for the maximum: will select the lowest value that is higher than all values in your data set. (See blue value in list)

You can also combine all methods. For example you can set the minimum value as 0 always and let RChart calculate the maximum value:

*Parameters*	*Description*	*Equivalent Java[TM] class/property*
YSCALE_MIN=0 YSCALE_EXACT_MIN=false YSCALE_EXACT_MAX=true YSCALE_PREF_MAXMIN=-1000000\|-500000\|-100000\|-50000\|-10000\|-5000\|-1000\|-500\|-250\|-100\|-50\|-25-10\|-5\|-1\|-0.5\|-\|0.1\|0\|0.1\|0.5\|1\|5\|10\|25\|50\|100\|250\|500\|1000\|5000\|10000\|50000\|100000\|500000\|1000000	Minimum is 0 Take max. value from the list of preferred values.	yaxis.scale.min yaxis.scale.exactMaxValue yaxis.scale.exactMinValue yaxis.scale.preferred_MaxMin_values

Logarithmic Scales

the following additional parameters are needed for logarithmic scales:

XSCALE_LOG, YSCALE_LOG and Y2SCALE_LOG. if "true" the scale will be logarithmic.
XSCALE_LOG_BASE, YSCALE_LOG_BASE and Y2SCALE_LOG_BASE. Base of the logarithm.
TICK_LOG_INTERVALY,TICK_LOG_INTERVALX and TICK_LOG_INTERVALY2. If "true" the ticks will be printed at logarithmic intervals (which is fixed intervals in the screen). If false the TICK_INTERVAL will be used to draw the ticks at fixed value intervals (not screen intervals).

Note: logarithmic scales do not accept negative values.

Example 1:

A base of 10 means that the distance between 1 and 10 will be the same as the distance between 10 and 100, 100 and 1000 ...

*Parameters*	*Description*	*Equivalent Java[TM] class/property*
TICK_LOG_INTERVALY=true YSCALE_LOG= true YSCALE_LOG_BASE=10 YSCALE_MIN=0 YSCALE_MAX = 1000	Ticks show not be placed at fixed intervals bu using logaritmic scale. Y Scale will use logarithmin scale base 10 minimum and maximum values	YAxis.logarithmicIntervals=true; YAxis.scale=logScale(); ((logScale) YAxis.scale).base=10; YAxis.scale.min=0; YAxis.scale.min=1000;

Example 2:

The default base is 2. This means, the distance between 1 and 2 will be the same as the distance between 2 and 4, 4 and 8..

*Parameters*	*Description*	*Equivalent Java[TM] class/property*
TICK_LOG_INTERVALY=true TSCALE_LOG=true YSCALE_LOG_BASE=2 YSCALE_MIN=0 YSCALE_MAX = 1024	Ticks show not be placed at fixed intervals bu using logaritmic scale. Y Scale will use logarithmin scale base 2 minimum and maximum values	YAxis.logarithmicIntervals=true; YAxis.scale=logScale(); ((logScale) YAxis.scale).base=2; YAxis.scale.min=0; YAxis.scale.min=1024;