Principal Components Analysis  PCA

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10.7

PCA plot

This window shows plots of the sample 

scores

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 and the 

eigenvectors

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. The

display options are selected from the panel below the graph.

The label radio box is used to select labelling for the samples. Select 

Title

 to

display on the plot the names of the samples. Select 

Number

 to show the

sequential number of each sample in the working data set. Select 

No labels

 to

remove labels from the plot.

The plot radio box allows sample scores, the eigenvectors (one for each species

or row in the working data ) or both to be plotted. If both are selected then the

biplot uses different axes to plot the scores and eigenvectors. The axes for the

scores are displayed at the bottom and on the left. Note that the eigenvectors are

labelled using column numbers used in the eigenvectors table. The display

cannot show labels and arrowheads so the eigenvectors are represented as lines

rather than vectors.

The axes displayed in the plot are selected using the Plot component (x) and Plot

component (y) drop down boxes. The default is axis 1 and axis 2, which will

display the relative positions of the samples with respect to the two largest

components.

This shows both the vectors for the variables (species) and the positions of the

samples within the first two axes of the ordination space.

The diagram was created using the demo dataset powerstation_fish.csv.

#perimeterIn two dimensional plotting it is possible to display the perimeter of

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