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help for ^kerneld^                                            (STB-27: snp6.2)
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Kernel density estimation
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    ^kerneld^ varname [^if^ exp] [^in^ range] ^,^ ^b^width^(^#^)^ ^k^ercode^(^#^)^ ^np^oint^(^#^)^
		[^g^en^(^densivar gridvar^)^ ^nog^raph graph_options]


Description
-----------

^kerneld^ calculates the density of ^varname^ using various univariate kernel
estimators.  By default, ^kerneld^ graphs the estimated density.


Options
-------

^b^width^(^#^)^ specifies the smoothing parameter (bandwidth or halfwidth) of the
    kernel. This parameter define the width of the weight function window
    around each grid point. The smoothness of the estimate can be regulated 
    by changing this parameter: wide intervals produce smooth results; narrow
    intervals produce noisier density values.

^k^ercode^(^#^)^ specifies the weight function (kernel) used to calculate the density
    according to the following codes:

        1 = uniform
 	2 = triangle 
 	3 = Epanechnikov
 	4 = quartic (biweight)
 	5 = triweight
 	6 = Gaussian
 	7 = cosinus

    Except for the Gaussian kernel, all the functions are supported on [-1,1].

^np^oint^(^#^)^ specifies the number of grid points at which the density is
    estimated.  Processing time increases quickly with the number of grid
    points.  However, if less than 50 grid points are used, the approximation
    may be too rough.

^g^en^(^denvar gridvar^)^ specifies two new variables to contain the estimated
    densities and corresponding grid points, respectively.

^nog^raph suppresses the graph.

graph_options are any of the options allowed with ^graph, twoway^.


Examples
--------

 . ^kerneld snow, bwidth(10) kercode(4) npoint(50)^

displays the quartic kernel density estimate of ^snow^ calculated at 50 grid
points.

 . ^kerneld snow, b(10) k(2) np(100) gen(dtri10 gtri10) nog^

calculates the triangular kernel density estimate of ^snow^ at 100 grid points
using a bandwidth of 10.  The density is stored in ^dtri10^ and the grid points
are stored in ^gtri10^.  The graph is suppressed.


Authors
-------

        Isaias H. Salgado-Ugarte, Makoto Shimizu and Toru Taniuchi
        University of Tokyo, Faculty of Agriculture,
        Department of Fisheries, Yayoi 1-1-1, Bunkyo-ku
        Tokyo 113, Japan.
        FAX:    81-3-3812-0529
        EMAIL:  fes01@@tzetzal.dcaa.unam.mx


Also see
--------

    STB:  STB-27 snp6.2, STB-26 snp6.1, STB-16 snp6
On-line:  help for @warpden@, @bandw@