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Inputing data to XLS-Biplot and saving files

Data in a simple rectangular matrix

To get a Biplot from your data, the simpler way is to prepare a text file with your data: simply put each case in a row, and put some space or tab to separate variable values. XLS-Biplot will interpret rows as cases (individuals) and columns as variables (characteristics). It is important not to have any missing data: all rows should have the same number of data numbers.

Any line that begins with any of the characters ! # % $ & ; ? @ will be completely ignored.

Conventionally, we use extensions ".dat" or ".tab" for these kind of files.

It is easy to make such a file if you have your data in an Excel spreadsheet. Select your data and choose Save as..., selecting the appropriate file type, usually "text delimited with tabs".

For example, loading a file that contains the following lines

4       6       6
5       3       0
5       3       1
5       6       7.5
5       4       2
5       6       8
5       7.5     4
5       7       4
6       3       2
6       5.5     4.5
6       6       6.5
6       7.5     4
6       7       1
6       5.5     5
6       7.5     2
6       6       4.5
6       2       3.5
6       7       1.5
6       2.5     6
6       7.5     11
produces a Biplot like this one:

Image abiplot

Data in full Biplot format

To fully specify a Biplot, a rectangular data array is not enough. Variables should have a name, some kind of analysis has to be chosen, etc. XLS-Biplot uses a special file format to read and/or save all this information.

In the examples folder you may find the file biplot-template.xls, an MS-Excel book that contain directions and a template to prepare a Biplot file for your data.

In the same folder, you should find a file scores.bpdata that can be used to produce the Biplot shown in section 1. Just go to the BiplotMenu menu and use Read data...

These are the first lines of this file.

Scores  PCA with normalization  UNDEFINED       UNDEFINED       UNDEFINED
132     3       Test    Ex1     Ex2
Symmetric Biplot
Case 0           4.000000000             6.000000000             6.000000000    
Case 1           5.000000000             3.000000000            0.0000000000    
Case 2           5.000000000             3.000000000             1.000000000    

The contents of a Biplot file should conform to the following description:

Line 1
Column 1
Name of the data set
Column 2
Analysis to be done to produce the Biplot, should be one of PCA with normalization, PCA without normalization, Simple CA, Logratio analysis, Ratio maps/Spectral analysis, None.
Column 3 and ff.
Type of variables, repeat as many times as variables.
Line 2
Column 1
Number of cases.
Column 2
Number of variables.
Column 3 and ff.
Names for variables, repeat as many times as variables.
Line 3
Column 1
Biplot type, should be one of Form Biplot, Covariance Biplot, Symmetric Map, Symmetric Biplot. The last is the default.
Column 2
Column 3 and ff.
Weights for columns, repeat as many times as variables, or left it blank.
Line 4 and ff.
Repeat as many times as cases.
Column 1
Name for the case.
Column 2
Weight for the case, or empty.
Column 3 and ff.
Data dor the case, repeat as many times as variables.

Options for 'Analysis' are (please type it carefully)

Getting output

From a Biplot window, you can save your work at three diferent levels: Saving the data file with most information embedded (using what we call "Biplot file format"), Saving a report on the Biplot currently in use or saving the complete window you are working with to reuse it later. Following subsections explain these options in detail.

Saving the data file

Use the item Save Biplot data... in the Save... menu (window toolbar) to produce a text file that will conform to the Biplot file format and so it will include, along with the data, the variable and case names, variable types, weights for cases and/or variables, kind of analysis to use to build the Biplot, and kind of Biplot coordinates to use. Full specification of the format can be found in section 4.2. The file will be tab-delimited, so it can be open, read and manipulated using Excel or a similar program.

Conventionally, we use the extension ".bpdata" for these files.

Saving a Biplot report

Use the item Save Biplot report... in the Save... menu (window toolbar) to produce a textual report of your Biplot. Usually this can be useful if you want to use some of the intermediate or final results of the Biplot computation in other software. Open the report with any text processor or even with Excel to use part of it.

Image bp-report
The Save Biplot report... dialog allows you to decide whether you want to see the report on screen or save it to a file. You can decide too what is to be included in the report (that can be really long in some cases).

Conventionally, we use the extension ".bpreport" for these files.

Saving the full Biplot window

Use the item Save XLS-Biplot object... item in the Save... menu on the toolbar to produce a file that will contain a full description of the window you are working with, including all the graphical properties of axis, points, arrows and labels along with your data and the properties of the Biplot itself.

Later on, you may use the item Load XLS-Biplot window... in the File... menu (or the BiplotMenu menu under Unix) to restore the saved window.

Conventionally, we use the extension ".bplsp" for these files.

next up previous
Next: Manipulating the Biplot on Up: XLS-Biplot User's Manual (Version Previous: What is a Biplot?
Frederic Udina