Develop Reference

How can I graph values that are incredibly small in Java?

Basically I am attempting to use JFreeChart right now to graph some values. The only problem is that the values are incredibly minuscule, e.g 7.069781E-13. I believe these values are too small for JFreeChart to display. How can I display these small values visually in Java in a line chart format?
It looks like this currently:
And I want to make it look similar to this:

I found a work around.
I simply multiplied all the values by a factor of 100 so the graph now looks similar to the one in the example. I will include a disclaimer in the legend saying the chart has been multiplied by a factor to clearly see the line chart.

Also consider these alternative:
Invoke setRange(), seen here, to expand the y axis in the area of interest.
Add suitable controls, seen here, to control y zoom.
Advise users how to use the mouse for zoom control, as shown here.

Android donut chart fill with multiple colors based on timestamp

I am looking for a chart which will show one circle around that time like 12:00, 01:00 like. Which fills with some colors based on time of activity.
I found this link Create Doughnut Chart Similar to Google Fit but it isn't fit for my requirements.
Please find image below. This is how I am expecting the chart.
Here these colors represent some activity based on timings. I have a set of data with a timestamp and it's activity type.
Can anyone suggest to me how I can draw this chart? Is there any example for this?
Edit
I found this link http://www.androidtrainee.com/draw-android-clock-pie-chart-with-animation/ to draw clock pie view. But stuck at point to set width and fill color like in above image. Right now it's fill different color based on time in full circle. But how do I set width to this clock to fill color and center part blank to show 08:40?

Since these are very specific requirements, it is likely that you will have to create your own custom view on Android. The SO you linked has a few promising libraries linked including fit-chart. The documentation isn't great, but it seems to support adding chart parts with values in 1% steps.
So you would only need to convert your duration data into percent of the circle by using 60 minutes or 12 hours as 100%.
Here is the relevant usage part of fit-chart:
Collection<FitChartValue> values = new ArrayList<>();
values.add(new FitChartValue(30f, 0x2d4302)); // 30f seems to represent 30%
final FitChart fitChart = (FitChart)findViewById(R.id.fitChart);
fitChart.setValues(values);
Another library that looks promising is MPAndroidChart that supports a detailed Pie Chart.
Regarding taking time into account: There are plenty of tutorials on how to draw an analogue clock that should include calculation on how to position the texts around the circle. Here is one SO creating a CustomClock View with multiple tutorials linked.
Regarding setting up your custom view, this 2d-donut-chart tutorial drawing a chart based on Path.arcTo covers all the needed steps.
If you need further help it would be helpful if you add your data structure and what you already tried. But I hope with these libraries and tutorials you can create your desired view.
Regarding updated question: I would suggest that you create your own custom view. My best suggestion is to continue by comparing the ClockPieView.onDraw with the draw methods of the other libraries I mentioned that do draw a doughnut graph with a hole. Research how text can be rendered as part of the onDraw with your specific positioning.

Heres a list of jQuery extensions to do this:
http://www.jquerybyexample.net/2014/02/jquery-html5-library-circular-piechart-graph.html

You can customize the Pie chart of MPAndroidChart library to create this. Here is a similar one created using it.
Here you will find the documentation of the library and this demo application is also helpful.
Here is a sample code you can try out after adding MPAndroid chart library to your project.
List<PieEntry> entries = new ArrayList<>();
//add data entries, 100 will be considered as a full circle
entries.add(new PieEntry(50, ""));
entries.add(new PieEntry(25, ""));
entries.add(new PieEntry(25, ""));
PieDataSet pieDataSet = new PieDataSet(entries, "");
PieChart pieChart1 = (PieChart)rootView.findViewById(R.id.pie_chart1);
pieChart.setMaxAngle(360);
//You can customize the pie chart in many ways to suit your need
pieChart.setCenterTextRadiusPercent(84);
pieChart.setRotationEnabled(false);
pieChart.setRotationAngle(180);
pieChart.setHoleRadius(60f);
pieChart.setDescription(null);
pieChart.setHoleColor(ContextCompat
.getColor(context,R.color.colorTransparent));
pieChart.setBackgroundColor(ContextCompat.getColor(context,
R.color.colorTransparent));
pieChart.setTouchEnabled(false)
pieChart.setDrawCenterText(true);
pieChart.setCenterTextColor(Color.BLACK);
pieChart.setCenterTextSize(16f);
pieChart.setCenterText(status);
//Add animation (optional)
pieChart.animateY(1500);
pieChart.invalidate();

Drawing a range column chart using DOT language or java or similar?

I want to draw a range column chart for my data, something similar to this.
Any suggestion?

GraphViz isn't suitable for this sort of chart - it draws graphs of the "nodes and edges" type, rather than this sort of style.
It looks like the "range column" chart is essentially a stacked bar chart with four elements in each stack, with the bottom element and third element drawn without borders and with a transparent fill. So, I'd suggest trying to use a conventional graphing library that gives enough flexibility of control over bar charts to produce what you want.

Remove an axis from JavaFX Chart

I've created a XYChart with numerical values different (for example temperatue with pressure) so I want to draw my own axeS just beside my chart. To do the following I've to unshow the YAxis, how should I do that ?

By using a trick: The Chart needs the Y Axis to remain in place so it knows where to render your content. You can, however, hide it. Hide the tick labels and set the axis' opacity to 0 using this code:
chart.getYAxis().setTickLabelsVisible(false);
chart.getYAxis().setOpacity(0);
The axis will still be there, but not shown.

I found that if I hid the chart using the following code:
chart.getXAxis().setTickLabelsVisible(false);
chart.getXAxis().setTickMarkVisible(false);
((Path)chart.getXAxis().lookup(".axis-minor-tick-mark")).setVisible(false);
Then I get about ~10 pixels less blank space on the bottom. IF the space was an issue for your application then you could use css offsets to correct it. This solution may have more predictable offsets.

SOLVED: I got this to work for sharing a common x-axis for two charts stacked vertically:
Create two charts, each with their own identical copy of the x-axis object, setting identical upper and lower bounds (optionally by binding).
Then hide the x-axis in the second chart like this:
chart = new LineChart<Number,Number>(xaxis2,yaxis2) {
{// hide xAxis in constructor, since not public
getChartChildren().remove(getXAxis());
// not getPlotChildren()
}
};
You'll want to set the widths of your y-axes to be the identical, e.g.
int w = 60;
yaxis.setMaxWidth(w);
yaxis.setMinWidth(w);
yaxis.setPrefWidth(w);
yaxis2.setMaxWidth(w);
yaxis2.setMinWidth(w);
yaxis2.setPrefWidth(w);

Which type of Jfreechart is more suitable for Histograms?

I am working with JFreeChart in order to show a Histogram Chart. My idea is to create a chart with 10 double bars, one bar of the pair in a different color. The 10 values will correspond to 10 weeks, so every week I will have 2 bars representing two different datasets.
For this purpose I tried with class BarChart, and it works, but I am not able to asign different colors to each dataset.
If anybody could help with assigning different colors to each bar it would be great. Maybe another class is more suitable than BarChart?

The appearance of the bars is controlled by the renderer assigned to the category plot of the bar chart.
With the BarRenderer you can change the colour for each individual bar with the setSeriesPaint() method.
You can access the renderer from the chart by calling getCategoryPlot().getRenderer() on your chart.

For arbitrary colors within a series, you can override getItemPaint(), as shown here.