(Kernel) Density Wizard

The Density Wizard provides a dialog-driven interface to the DENSITY instruction, for computing the density function for a series of data using kernel methods.

Note: If you want to display a histogram for a series, use the Series Window and Histogram operations on the View menu.

Selecting (Kernel) Density from the Statistics menu brings up the following dialog box:

Series

Select the series you would like to examine from this drop down list.

Sample Start and End

Use these fields to set a specific starting and/or ending date for the estimation.

Density Estimates

Provide a series name here for the estimates of the density function.

Grid Series (X Values)

Provide a series name here for the "X" values at which the density is being evaluated.

Grid Setup

Select "Generate automatically" to have RATS generate the grid values and store them in the Grid Series. Choose "Use values already in series" if you are supplying an existing series with the Grid Series field and want RATS to use those values.

Number of Grid Points

If using the "Generate automatically" choice for Grid Setup, this field will appear allowing you to provide the desired number of grid points.

Create Graph

If you turn this switch on, RATS generates a SCATTER instruction doing a line graph of the estimated density.

Window Type

Use these fields to select the kernel bandwidth and window type. For the bandwidth, you can enter a value or leave this field blank to use the default value. Use this window type field to choose the type of window used: "Epanechnikov", "Triangular", "Gaussian", "Logistic", "Flat", or "Parzen".

Relative Smoothing

Specific Bandwidth

By default, DENSITY chooses a bandwidth based upon sample statistics for the series which has certain optimality properties. However, to the eye, this tends to be too narrow, leading to a density estimate which is less smooth that would be expected. The Relative Smoothing field allows you to increase the bandwidth proportionally to that. If, instead, you want a Specific Bandwidth, use the appropriate box for that. (If you put a value in Specific Bandwidth, that is what is used, so make sure it's blank if you want to use the Relative Smoothing.