Principal Components Analysis

Description

Principal components analysis transforms a set of potentially correlated variables into a new set of uncorrelated variables. These new variables or "principal components" are linear combinations of the original variables and are chosen in a way to maximize the fraction of variability in the original data. See statistics textbooks for further details (e.g., Wilks 2006). This tool performs principal components analysis on a set of entered data and outputs the eigenvalues, loadings, and scores under "Results" and to three output files. The main output file specified by the user contains the eigenvalues. A second output file contains all of the loadings, and has the word "Loadings" appended to the end of the name. A third output file contains all of the principal component scores, and has the word "Scores" appended to the end of the name. Plots of the eigenvalues, loadings, and scores can also be made by selecting the "Eigenvalues", "Loadings", or "Scores" tab and clicking the "Plot" button.

Input

File
Select the input data to analyze by clicking on "Browse" and navigating to the proper file.

Input Data Format
Year / Data

Each "/" is a tab (i.e., data should be tab-delimited). Missing Data should be denoted as "-99".

Start Row
This input is the row number where the main data to be processed begin in the input file selected above. An example of how row numbers are entered is shown in Figure 2 located in the Running Dendro Tools topic.

Start Year
Enter the year to start the analysis.

End Year
Enter the year to end the analysis.

Number of Variables
Enter the number of variables located in the input file.

Perform Varimax Rotation
Check the box to perform varimax rotated principal components analysis. Rotated principal components analysis is typically done after the regular principal components analysis is completed. This allows the user to assess the eigenvalues and select a lower number of principal components to output. Dendro Tools will ask for the "Number of Principal Components to Output".

Output

File
Select or enter the name of the file where the results will be stored.

Header
Information entered here will be output in the first line of the output file.