A2 Databases

Databases are becoming indispensable when data sets of increasing size are analysed. JUICE (Tichy 2002) and TURBOVEG (Hennekens & Schaminee 2001) are probably the best known. I used VEGEDAZ (Kuchler 2009), a program with features typical for the purpose. The functions mentioned below refer to this, but all databases designed for handling vegetation data do so similarly:

• There are functions to test input data, such as format of date, double entries in releve and species labels, range of variables, double entries of entire releves and species vectors, identification of outliers (Section 11.3) and so on.

• There are tools for data exploration, mainly options for display of scatter plots and frequency diagrams.

• Further, one of the functions concerns the data selection used for example when double entries have to be erased. Subsets may be generated based on stratification criteria (Section 2.3.2). Reduced samples are derived using systematic or random subsamples, as shown in Section 11.2.

• The program also supports handling of taxonomic problems existing in all fields of organismic biology (plants, animals, fungi, algae, bacteria, etc.). For all species names, alternative names are displayed for selection; names form different taxonomies - outdated as well as valid ones. This function is essential for combining data sets, as in Chapter 12.

• Further support is given by providing auxiliary variables, mainly valid for the geographical area considered, such as political borders, rivers, digital terrain models and, in the present case, indicator values of Central Europe (Landolt 1977), as used in Section 11.4.

• The program package is also an analytical tool. Many basic functions used throughout this book are implemented in the program menu. Furthermore, there is an interface to the R statistical package, where, for example, all functions of the VEGAN package (Dixon 2003) and others are available. Output of R programs, like ordination coordinates and classifications, can be embedded into the data set being analysed.

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