setGridLinesVisible() problem

[Rudra A Dixit]

Hi DG,

I checked out the setGridLinesVisible() method, but it's only showing horizontal grid lines, not vertical. Here's the full description of my problem:

I'm generating a PNG image to display on a JSP. I've got a maximum image width limit of 420 pixels. When I query for long intervals (for example: from 01/15/2002 01:00 to 01/23/2002 23:00), JFreeChart produces the graph, but the X-Axis displays only one label (in my case, it's 01/21/2002). The person who is studying the generated graph has to guess the other dates, since there aren't any other X-Axis labels available. I guess this happens because of the image width limit.
Therefore, if I have vertical gridlines, this would help the user understand more precisely what is being demonstrated.
I'm not sure if I have been clear now. Please let me know so that I can solve any doubts.

Thanks in advance,

Rudra A Dixit

[David Gilbert]

Hi Rudra,

I think what is happening is your date axis is (auto) selecting a tick unit of 1 week, because it doesn't have room to display the labels for 1-day tick units (the next smallest size). You could try a couple of things:

(1) HorizontalDateAxis.setVerticalTickLabels(true). When the labels are vertical, you can fit more of them in (but you get less plotting space).

(2) Edit the code in DateAxis. Add a new entry (or several) in standardTickMagnitudes, standardTickUnits and standardTickFormats. If you add a tick unit for 2 days, between 1 and 7 days, that might solve your problem.

Otherwise you will have to wait until I get minor tick units implemented...

Regards,

DG.

[James Kim]

Hi,

Currently the method setShowGridLines() in ValueAxis does not work properly when trying to display horizontal grids from HorizontalDateAxis with the following error:

java.lang.IllegalArgumentException: null Stroke
at sun.java2d.SunGraphics2D.setStroke(SunGraphics2D.java:801)
at com.jrefinery.chart.HorizontalDateAxis.draw(HorizontalDateAxis.java, Compiled Code)
at com.jrefinery.chart.XYPlot.draw(XYPlot.java, Compiled Code)
at com.jrefinery.chart.JFreeChart.draw(JFreeChart.java, Compiled Code)
at com.jrefinery.chart.JFreeChart.createBufferedImage(JFreeChart.java:506)
at com.jrefinery.chart.ChartUtilities.writeChartAsJPEG(ChartUtilities.java:101)

Here is a fix:

There are 4 constructors for HorizontalDateAxis. The last 2 arguments are set to null by default and this is causing the issue. Replace these 2 nulls with "ValueAxis.DEFAULT_GRID_LINE_STROKE, ValueAxis.DEFAULT_GRID_LINE_PAINT". Re-compile the library and enjoy your graph.

(It took awhile to figure this out...)

-JYK

[David Gilbert]

Hi James,

Thanks for the report. It looks like I've already fixed this, but I want to be sure so can you tell me what version of JFreeChart you are using?

Regards,

Dave Gilbert

[James Kim]

I am using jfreechart-0.7.0.jar.

-JYK

[David Gilbert]

Thanks. I think you will find it is fixed in a later version. If not, let me know and I'll look at it again.

DG.