** Next:** Inputing data to XLS-Biplot
**Up:** XLS-Biplot User's Manual (Version
** Previous:** Basics of XLS-Biplot

**Subsections**

#

What is a Biplot?

Biplots are statistical graphics that represent in the same plane both the
variables and the cases. Usually variables are represented by arrows, while
points represent cases. See the example in 1.

A Biplot can be constructed from a data matrix, where conventionally each
column represent a variable, and each row includes the variables value
for a given case.

The general layout of the computations is:

##

Kinds of analysis, kinds of biplots

According to the previous scheme of the computations, there are several
possibilities for the construccion of a Biplot. Some of them are more usual,
and we include four of them as "Canned analyisis". They are accessible via the
*Define data processing...* in the *Biplot...* menu button.

**PCA without normalisation**
- centring of columns SVD, etc...
**PCA with normalisation**
- centring of columns normalisation
of columns SVD, etc...
**simple CA**
- transform to Pearson contingency ratios
apply row and columns masses
(weighted) double-centring (weighted) SVD, etc...
**logratio analysis (Aitchison)**
- transform to logarithms
double-centring SVD, etc...
**ratio maps (Greenacre, or spectral mapping, Lewi)**
- transform to
logarithms apply row and column masses
(weighted) double-centring (weighted) SVD, etc...

There are three types of coordinates (Standard, Principal, and Canonical), and
four standard Biplot/map options that are accessible through the *Biplot type*
item in the *Biplot...* menu button.

Asymmetric map (form Biplot) of the rows.

Asymmetric map (covariance Biplot) of the columns.

Symmetric map (not a Biplot).

Symmetric (*canonical?*) Biplot.

** Next:** Inputing data to XLS-Biplot
**Up:** XLS-Biplot User's Manual (Version
** Previous:** Basics of XLS-Biplot
*Frederic Udina *

2005-03-15