Creating data
subsets by applying filters
Statistical
Functions on Plotted Data
VOPlot 3D (VOTable 3D Plotting tool) is an applet for plotting different astronomical graphs using data stored in VOTable format. It supports different operations such as rotation, panning and zooming on the plot. VOPlot is available in desktop and webbased version.
Click here for Release Notes and disclaimer information.
About VOPlot
VOPlot 3D has been developed as a part of the Virtual Observatory  India initiative by Persistent Systems and the InterUniversity Centre for Astronomy and Astrophysics (IUCAA). The VOIndia project is supported by the Ministry of Information and Communication Technology of the Government of India.
VOPlot 3D uses Java 3D API (v1.3.1) for plotting different astronomical graphs in threedimension. Java 3D is a standard extension to the Java 2 JDK. It is an interface for writing programs to display and interact with threedimensional graphics.
3rd Party Tools implemented:
· SAVOT (Simple Access to VOTable): VOPlot 3D uses SAVOT (Simple Access to VOTable) to read VOTable documents.
· Colt: VOPlot 3D uses Colt libraries from CERN for statistical calculations of the VOTable data.
· Ptplot (v5.2): VOPlot 3D uses Ptplot (v5.2) for display of Box Plot.
Standalone Version:
* To use the standalone version of VOPlot, you will need to download the executable jar file named voplot3D.jar. The file can be executed by typing the following command at the command prompt:
java jar voplot3d.jar 
This will open a java application window as shown in the Figure 0.
To use data from a VOTable you will need to load it first. You can specify the path of a VOTable on your personal computer (PC) by clicking on the "Open" submenu from the "File" menu. The message on the status bar will indicate whether the file was loaded successfully or not.
* To see the version of JRE installed, type the following command at the command prompt:
java –version 
* To increase the memory of JVM to 64 Mb, type the following command at the command prompt:
java –Xms64m jar voplot3d.jar 
Click here for installation instructions for Java 3D API.
Note: To run VOPlot 3D version1.0, you must have Java Runtime Environment (1.4 or later), Java 3D API (1.3.1) OpenGL 1.1 or DirectX (8.0 or later) is required.
Loading Data In VOPlot 3D:
Currently VOPlot3D uses data in VOTable format for plotting. The default columns for the graph are loaded on the basis of FIELD UCDs. Once the table is loaded, the metadata of the VOTable is read and the numeric columns are retrieved and listed in the combo boxes for X, Y and Zaxis on the control panel.
Web Version:
To draw a plot of one columns against the other,
You can see the scatter plot. If required, you can plot data points on a log scale by setting the option appropriately using the "Log" checkbox.
Figure 2
To change the plot properties click on the " View > Plot Properties" menu, which opens the "Change Plot Properties" dialog as shown in Figure 3.
The various plot properties such as Title of the plot, Xaxis label, Yaxis label, Zaxis label, Xaxis range, Yaxis range and Zaxis range can be changed.
Figure 3
Following keys can be used for zooming and panning of the plot.
Sr. No. 
Key 

Effect 
1. 
Up Arrow key 

To zoom out of the graph 
2. 
Down Arrow key 

To zoom in to the graph 
3. 
Home Key 
Home

Reset graph to the centre 
4. 
Left Arrow Key 

For left lateral translation 
5. 
Right Arrow Key 

For right lateral translation 
6. 
Page Up Key 
PgUp

To move the graph up 
7. 
Page Down Key 
PgDn 
To move the graph down 
Note: ZoomingIn and ZoomingOut of the graph is restricted up to a certain depth.
To rotate the Plot in any direction, press the left mouse button on the graph and move it in required direction of rotation. On rotation of the graph, the corresponding euler angles (theta, phi and psi) are displayed in radians on the top righthand corner on the control panel.
Euler angles’ panel is shown in Figure 4 below.
Figure 4
The plot in 3D VOPlot can be rotated about X, Y or Zaxis using the mouse to get any desired projection. The amount of rotation involved (change in the ‘line of sight’) is represented in terms of Euler angles, Θ (theta), Φ (phi), Ψ (psi), which are angles of rotation about the X, Y and Zaxes in that order. Corresponding Euler angles for any projection are displayed on the upperright corner on the control panel as shown in Figure 4 above.
It is possible to get the projection of the plot by providing the corresponding Euler angles as well. For this, the Euler angles can be specified in ‘Specify line of sight’ dialog under View>Enter Line of Sight as shown in Figure 5 below.
Figure 5
To overlay plots (simultaneously viewing multiple plots with similar range on the same axes system)
You can see the second plot overlaid on the first one if the second one is in the same range as the previous one. Only that portion of the second plot is visible that is within the already plotted range.
To see the entire range of points, click on the ‘Show full range of data’ button ( ) in the toolbar on control panel. To reset the plot to the previous range, click on the ‘Reset axis ranges’ button ( ).
A screen shot of overlaid plots can be seen in Figure 6 below.
Figure 6
A different marker color will be used for each plot, to allow one to differentiate between the plots. Currently 16 datasets can be overlaid.
One can create new columns by defining transformations on them. You can use expressions with arithmetic operators, trigonometric functions, and miscellaneous functions shown below to create new columns. You can use transformed columns for plotting.
+ 
Addition 
 
Subtraction 
* 
Multiplication 
/ 
Division 
log(a) 
Log to the base 10. 
ln(a) 
Natural Log of "a" with base e, where e is Euler's number (i.e. 2.718...). 
pow(a,b) 
"a" raised to power of "b". 
sqrt(a) 
Square root of "a". 
exp(a) 
Returns the exponential number e (i.e. 2.718...) raised to the power of "a". 
dexp(a) 
10 raised to the power of "a". 
cos(a) 
Trigonometric cosine of an angle. a = an angle in radians. 
acos(a) 
Computes the arc cosine of "a". "a" must range from 1 to 1; the resulting angle is in radians and will range from 0 to pi. 
sin(a) 
Trigonometric sine of an angle. a = an angle in radians. 
asin(a) 
Computes the arc sine of "a". "a" must range from 1 to 1; the resulting angle is in radians and will range from pi/2 to pi/2. 
tan(a) 
Trigonometric tangent of an angle. a = an angle in radians. 
atan(a) 
Computes the arc tangent of "a". The resulting angle is in radians and will range from pi/2 to pi/2. 
toradians(a) 
Converts an angle measured in degrees to an equivalent angle measured in radians. 
todegrees(a) 
Converts an angle measured in radians to an equivalent angle measured in degrees. 
The dialog box for creating new columns is shown in Figure 7.
Figure 7
You can create new data subsets by defining filters on them. You can use a condition with relational operators and logical operators with operators and functions shown above to create new data subsets. Data subsets can be used for plotting.
< 
Less than 
<= 
Less than or equal to 
> 
Greater than 
>= 
Greater than or equal to 
== 
Equal to 
!= 
Not equal to 
&& 
And 
 
Or 
! 
Not 
The dialog box for creating data subsets is shown in Figure 8.
Figure 8
Once a data subset is created you can plot data from the subset. This can be done by choosing the data subset from the Filters combo box in the main applet window.
Note: "None" represents the complete data. Only data points satisfying the filter condition will be considered for plotting.
Statistical functions can be applied on the plotted data.
The dialog box is divided into two tabs – basic and advanced functions. The basic functions require only one data array, while the advanced functions require two or three data arrays as parameters.
The following statistical functions are currently supported.
Sr. No. 
Function name 
Input Columns 
1 
Number of observations 
X 
2 
Range 
X 
3 
Minimum 
X 
4 
Maximum 
X 
5 
Mean 
X 
6 
Variance 
X 
7 
Standard deviation 
X 
8 
Skew 
X 
9 
Kurtosis 
X 
10 
Linear correlation 
X, Y 
11 
Significance (t) for Linear correlation 
X, Y 
12 
Probability for Linear correlation 
X, Y 
13 
Rank correlation 
X, Y 
14 
Partial correlation 
X, Y, Z 
VOPlot takes the entire data range into consideration while evaluating the statistical functions. This will evaluate the statistical functions for the currently plotted columns, along with the applied filter, if any, in the current axes ranges. Sample dialog box with basic tab selected showing plot statistics is shown in Figure 9.
Figure 9
Sample "Advanced Functions" tab is shown in Figure 10.
A Box plot provides an excellent visual summary of many important aspects of a distribution. It identifies the middle 50% of the data, the median and the extreme points.
Click on the "Box Plot" button on the "Plot statistics" dialog to display the Box Plot for the X column. Sample Box Plot is shown in Figure 11 below.
Figure 11
The VOTable data used to plot the graph can be displayed in tabular format. It also displays the filters and data sets that are userdefined.
To view the VOTable data, click on "Data in Table format" submenu from the "View" menu. The "Display Data" dialog box will open.
The data is displayed in two different tables. The first table displays the field metadata of the VOTable, while the second table displays the actual data.
If points are not selected on the plot, the entire plot data is displayed.
Sample dialog box
displaying the selected data and metadata of the VOTable is shown in Figure 12.
Figure 12
Used to display Plot data in VOTable format. It also displays the filters and data sets that are userdefined.
To view the VOTable, click on "Data in VOTable format" submenu from the "View" menu. The "Display VOTable" dialog box will open.
Sample dialog box displaying VOTable containing data of selected points is shown in Figure 13 below.
Figure 13
This feature is available only in the desktop version of VOPlot. To save a VOTable, click on "Save As File" button on the dialog box. The save as dialog box will appear. Select a file and click on OK. The file is saved as an XML file, VOTable format. The various userdefined filters and data columns pertaining to all points (more than 100) are saved in the file.
Note: This feature is not
available in the webbased version of VOPlot.
We would be happy to receive any feedback/comments on 3D VOPlot. For feedback and comments please contact voindia@vo.iucaa.ernet.in.