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SAS/SPECTRAVIEW Software User's Guide

Displaying Response Values as a Point Cloud

One of the first steps in analyzing data is to examine all the data values, for which the point cloud is ideal, for example, to show concentrations of data. A point cloud displays response values as colored markers, showing individual data points. The marker locations represent the plotted values of the X, Y, and Z variables, and the color of each marker represents the range in which that value resides as mapped in the data ramp.

You can display all response values in a point cloud, or you can specify a subset by using the response histogram.

Subsetting Response Values

Using the response histogram, you can specify a subset of response values for a point cloud by setting a range of responses. The response histogram, which appears at the bottom left of the interface when you request a point cloud or an isosurface, displays the frequency distribution of data points that share the same response value. The histogram may also include software-interpolated values between the actual response values.

Response Histogram to Subset Point Cloud


There are actually two histograms:

Displaying a Point Cloud

  1. Select [Tools], [Planes], then [Point cloud].

  2. To change the shape of the marker, select one from the panel of choices, which include a period, an X, an asterisk, a O, and a +. The default is the asterisk.

  3. To change the size of the marker, move the slider below the label MARKER SIZE. The default is a moderate size marker. The larger the marker size, the more solid the point cloud.

  4. To specify a subset of response values displayed in the point cloud, use the response histogram located in the lower left of the interface:

    Note that you can modify subsetting criteria with a point cloud displayed, but for a lot of data, you may want to turn off the point cloud to speed up the process.

  5. Select [On].

The following point cloud displays a subset of response values from the EPA data set:

Point Cloud Displaying Location of High Sulfate Concentrations


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