iReport line chart category label - charts

Question

i'm using the Line Chart component to generate a chart based on the consumption of a building.
Imagine a possible chart based on the consumption of a building in a period of a month and a resolution of a day. It will have 30 points of consumption corresponding to 30 days.
The problem is with the category axis labels. With a considerable amount of points, the labels becomes unreadable. How can i just label some points?
My best regards

Answer 1

Don't use a "Line" chart. Instead use a "Time Series" chart.
It automatically handles the issues around charting all points but only labeling a readable number of them. It also handles problems created by data points that are not uniformly spaced.
EDIT: If your incoming data is a String instead of a Date, then you have extra work. Time Series charts expect Times (well, Dates). You'll need to cast your DateString into a real Date. But the work is small, and the benefits are large. Use a variable like this: new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse($F{MyDateString}).

Answer 2

Use this code to generate a label on the line chart in JASPER report
else if(jasperChart.getChartType() == JRChart.CHART_TYPE_LINE) {
LineAndShapeRenderer line = (LineAndShapeRenderer) chart.getCategoryPlot().getRenderer();
line.setBaseItemLabelsVisible(Boolean.TRUE);
line.setBaseItemLabelGenerator((CategoryItemLabelGenerator) new StandardCategoryItemLabelGenerator());
}