Graphics Reference
In-Depth Information
Figure
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OECD countries with respect to the first three principal components
Whenthenumberofvariables andstatistical units remains moderate,statisticians
very familiar with data analysis have a good opportunity to make correct interpreta-
tions taking into account these aspects. When the number of units and/or variables
increases, itbecomes hardanddi
culttoobtain a goodinterpretation. However,ba-
sic geometric principles still hold, and we move throughout the interpretation on the
basis oftheconcepts “close” and“far”.Closepoints identify units with similar figures,
while far points refer to units with clearly different characteristics.
Supplementary units and supplementary variables
here is a very important property pertaining to all FAs that is rarely commented
upon in textbooks on multivariate analysis: the possibility of representing supple-
mentary units and/or supplementary variables. Having the means to produce inter-
activegraphicalrepresentations,thisfunctionalityallowsonetoadd and removesub-
sets of statistical units and variables in graphical visualization in order to evaluate
their position with respect to the others. In exploratory analysis, deletion of extreme
points allows the analyst to evaluate the axes' stability.
