DataLab is a compact statistics package aimed at exploratory data analysis. Please visit the DataLab Web site for more information....

## PCA Biplot

The bi-plot shows both the loadings and the scores for two selected components in parallel. Please note that both the scores and the loadings are scaled to a maximum value of 1.0. A line from the origin to each loading point is drawn to emphasize possible groups of variables. The numbers at the loading points correspond to the variable indices.

 Hint: If you want to know which point (either score or loading) represents which object or variable, you simply move the mouse cursor over the interesting point. The object or variable name along with the coordinates of the selected point are displayed in the info box at the bottom of the PCA window.

Left to the bi-plot there are several controls for changing the display options. In addition to the selection boxes for choosing the principal components to be displayed there are several buttons which provide the following functionality:

 show all data Clicking this button sets the zoom factor to the standard value so that all available data points are shown in the diagram. mouse action Depending on the state of this button (indicated by its icon) the mouse can be used for zooming, panning, or marking the data. Clicking the button toggles its function: Window: any rectangular region of the chart can magnified to fit the full area of the chart by simply pressing and holding down the left mouse button at one corner of the region. Moving the mouse now shows a rubber band rectangle. The area of the rectangle is blown up to the full chart area when the left mouse button is released. Drag: the scale of the chart can be increased or reduced by pressing and holding the left mouse button. The scaling factors of the x and y axes are changed in proportion to the movement of the mouse (up and right = magnify, left and down = reduce). Pan: the visible part of the chart can be shifted by pressing and holding down the left mouse button. The chart follows the mouse movement which results in panning the visible window across the data. Mark Data: Data may be marked by activating this option. In order to mark one or more data points you have to draw a rectangle around these points. Marked data are indicated by red crosses. A detailed description can be found in the section "marking the data". unmark data Data which have been marked previously can be unmarked by clicking this button. setup Clicking this button allows to adjust various plot parameters (such as the colors or symbols).

Last Update: 2012-Jul-25