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From |
Austin Nichols <austinnichols@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st:kdensity (1) at percentile level (2) select bandwidth to compare across two groups |

Date |
Fri, 6 May 2011 12:39:58 -0400 |

Amanda Fu <mandy.fu1@gmail.com>: I recommend you start with . findit akdensity and read the linked paper http://www.stata-journal.com/sjpdf.html?articlenum=st0037 for examples. On Fri, May 6, 2011 at 12:28 PM, Amanda Fu <mandy.fu1@gmail.com> wrote: > Hi all, > > I wonder if someone could help me with two questions related to -kdensity-. > > (1) I want to use -kdensity- to estimate a variable 's kernel density > at percentile level. If I use > pctile x_pcile=x, n(100) > kdensity y, at(x_pctile) g (a1 a2) > > I find the variable x_pctile (as well as a1 and a2 ) only has 99 cases > with values for percentiles. But the left observations all have > missing values. > Do I need to create a variable that indicate the percentile value for > each observation so that each case has a nonmissing value? Is it OK > just use x_pctile as above? > > (2) I want to compare the kernel density curves of a variable for two > groups. So I need to select a same bandwidth for the estimation for > the two groups instead of using the optimal default option. But how > should I choose the bandwidth? * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st:kdensity (1) at percentile level (2) select bandwidth to compare across two groups***From:*Amanda Fu <mandy.fu1@gmail.com>

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