The color of the pixel is normally derived from the position of the last found fitting data location. The databases are scanned bottom-to-top, then left-to-right. Green represents the lower left corner of the datasets, red the upper left, cyan the lower right, and magenta the upper right. To see more detail, depress and hold down the Color button on the application.

Alternatively, the scatterplot can display a color based on the number of data values fitting into the bin. To get this type of display, toggle the Frequency/Position button.

Scatterplot also calculates statistical information about the data sets. Several choices of information can be made; see below for more details on that.

Controls

Buttons

Save Stats stores all the statistical information computed in a file (stats.dat).

Frequency is a toggle between the default display in which pixels are colored by original position within the data sets and a histogram-like frequency coloring.

Menus

"None" is the fastest; no statistics are computed or displayed. This is most useful for interactive scatterplot work. "Basic" stats are the default; they include: means and standard deviations for each of the data sets, and the correlation coefficient (R) between the two data sets. "X moments" shows the mean, standard deviation, average deviation, skew, and kurtosis for the horizontal data set. "Y moments" does the same for the vertical one. "Linear Regression" does a least-squares fit to the data and displays the correlation coefficient, the slope and y-intercept of the fitted line (and error bars on it) as well as the number of points in the sample and the sum of the squares of the residuals (SSR) (useful in doing one's own stats). See below for definitions of all these statistics.

The main menu allows one to control a bounding box in the application and to control how sliders interact with the application. The bounding box controls are similar to those in Image except that no crosshair exists.

"Freeze Horizontal Slice" and "Freeze Vertical Slice" are switches that, when on, prevent a database's slice selection from changing. This is most useful when scattering a database against itself; one need only link in one slider, freeze an axis at the desired level, then change the other one.

Applications to Connect to This Application

Any application with a bounding box (e.g. Image) will allow 2D Scatterplot to limit its scope to a portion of a data set. These objects must be connected via the "drag 'n drop" button to scatterplot.

Color tool will change the colors of the display in Frequency mode, as will Histogram.

Sliders will control which slices are used to compute the scatterplot. If one slider is linked in, that slider will control each data set's level. If two are linked in, they will control the two data set levels independently.

Applications to Connect This Application to

Tricks and Gotchas

Appendix: Definitions of Statistics