Logarithm axes problems

nclemeur · Post by **nclemeur** » Mon Feb 14, 2005 12:51 pm

Hello,

First of all I would like to congratulate the JFree team for producing such an amazing toolkit. I was desesparetely looking for something similar in C++ (free and cross-platform), and never found! So now I am a Java addicted (and newbie).

I am still discovering the tools but I found a few glitches in the logarithmic axes, and I was wondering if anyone have some solutions or can suggests me in which direction I should look... I am also not sure if this is the correct place to post these emails. If not please correct me.

I have a XYPlot in ChartPanel with 2 logarithmic axes. I have the following problems:

o The tick labels on the Domain Axis are not displayed in the good format: I have 1e-3 altough I use setExpTickLabelsFlag(true). The problem is not present for the Range Axis;

o The tick label is a bit strange on the Domain Axis: I have for example (1e-3 2e-3 1e-2 2e-2,...). Again this problem is not present on the Range Axis

o The Zooming does apparently not take into account the fact that this is a logarithmic plot. If I have a range from 0.01 to 100 after zooming out I have -100 to 100 (or something similar, I can't really remember) where I would expect 1e-4 to 1e4....

If necessary I can provide a snapshot altough I am not to sure how to do this in this forum.

Any suggestion to where I should concentrate my search would be greatly appreciated.

Cheers

Nicolas

Guest · Post by **Guest** » Mon Feb 14, 2005 5:36 pm

As far as I know, a Domain Axis isn't a sorted Axis. It's just a collection of items.

So that explains chy the items on your domain axis aren't sorted: they just appear in the order you have added them.

Only solution I have found so far is writing my own function to sort the dataset, using the built-in Java sorting functions (Collections.sort).

Guest · Post by **Guest** » Mon Feb 14, 2005 11:32 pm

As far as I know, a Domain Axis isn't a sorted Axis. It's just a collection of items.

I am not sure what you mean by that. I used the terminology Domain Axis because it seems that this is the terminology used in JFreeChart for the X-Axis, but it was about the X-Axis an instance of Logarithmic Axis in a XYPlot I was refering. And everything is well ordered. So I don't think this is linked to what you are mentioning.

Cheers

Nicolas

nclemeur · Post by **nclemeur** » Tue Mar 22, 2005 11:29 am

Hello,

I have looked a little bit on this problem by examing rapidly the code in JFreeChart latest version and I think the problem is that the Log Axes needs to subclasse a few more methods in LogarithmicAxis.java. For example, the method zoomRange is not defined in this class and the method from valueAxis is therefore used... Which only deal with linear plot. Using the following code solve the problem:

Code: Select all

public void zoomRange(double lowerPercent, double upperPercent) {
        double start = Math.log10(getRange().getLowerBound());
        double end = Math.log10(getRange().getUpperBound());
        double length = end - start;
        Range adjusted = null;
        if (isInverted()) {
            adjusted = new Range(Math.pow(10,start + (length * (1 - upperPercent))), 
                                 Math.pow(10,start + (length * (1 - lowerPercent))));            
        }
        else {
            adjusted = new Range(
                Math.pow(10, start + length * lowerPercent), 
                    Math.pow(10, start + length * upperPercent));            
        }
        setRange(adjusted);
    }

(Please note that the isInverted case is not tested)

Another minor problem, is the use of DEFAULT_LOWER_BOUND in autoAdjustRange. This lead to zero for the axis origin if there are no data on the plot. I think it would be nice to have a DEFAULT_LOG_LOWER_BOUND defined to something like 0.001 or similar.

There are some other few problems with log axes, but I don't have really the time to investigate. Is there any plan to improve this classe before the official release 1.0?

Cheers

Nicolas

[/quote]

berth · Post by **berth** » Wed Mar 15, 2006 10:59 am

I have posted a subclass that fixes the zoom problem for JFreeChart 1.0.1 at

http://sourceforge.net/tracker/index.ph ... tid=115494

Post by **david.gilbert** » Wed Mar 15, 2006 3:43 pm

Thanks, I will try to have a look at this.

petersk · Post by **petersk** » Tue Mar 28, 2006 4:13 pm

Dave,
Is there any way to just incorporate the LogarithmicAxisPatched code on the sourceforge web site into the "real" LogorithmicAxis so others don't have to go through this pain?
Kurt

www.jfree.org