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help for ^adjksm^, ^lorobwei^, and ^roblowes^                  (STB-25: snp8)
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Programs for robust scatterplot smoothing     
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        ^adjksm^ yvar xvar [^if^ exp] [^in^ range] [^,^ ksm-options ]

        ^lorobwei^ yvar ysmooth

        ^roblowes^ yvar xvar bwidth


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

These three programs modify and augment Stata's ^ksm^ command.  ^adjksm^ is
identical to ^ksm^ except that the bandwidth of the smoother is constant along
the x-axis.  ^lorobwei^ and ^roblowes^ are used together to perform iterations
of Cleveland's lowess smoothing procedure.  ^lorobwei^ and ^roblowes^ implement
Cleveland's robustness weights, a feature currently not included in Stata's
^ksm^.  See help @ksm@ for general information about scatterplot smoothing.


Options
-------

^adjksm^ uses the same options as @ksm@.  See help @ksm@ for information.

^lorobwei^ and ^roblowes^ do not take any options.


Remarks
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Several steps are required to calculate a lowess smooth using these programs.
First, an initial estimate of the smooth is calculated by ^adjksm^.  This
estimate is used as an input to ^lorobwei^, which calculates robustness
weights according to the bisquare weighting function.  These weights are
stored in a new variable called ^robwei^.  As a consequence, you must not have
a variable with that name in your data set when you use ^lorobwei^.  Then the
next iteration of the smoothing process is performed by ^roblowes^, which
stores its output in another new variable called ^lowerob^.

In schematic form, here is the sequence of steps required:

  . ^adjksm y x, bwidth(.5) lowess gen(y0)^     /* y0 = initial estimate */
  . ^robwei y y0^                               /* robwei generated      */
  . ^lorobwei y x^                              /* lowerob generated     */
  . ^rename robwei w0^                          /* save initial weights  */
  . ^rename lowerob y1^                         /* y1 = next estimate    */
  . ^robwei y y1^                               /* begin 2nd iteration   */
  . ^lorobwei y x^                              /* and so on ...         */


Authors
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        Isaias H. Salgado-Ugarte 
        Makoto Shimizu
        University of Tokyo
        Faculty of Agriculture
        Department of Fisheries 
        FAX:  011-81-3-3812-0529


Also see
--------

    STB: STB-25 snp8
 Manual: [5s] ksm
On-line: help for @ksm@