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st: kdensity with binned data


From   Amy <dartmouthemails@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: kdensity with binned data
Date   Sat, 26 Jun 2010 00:45:08 -0700 (PDT)

Hi,

I have aggregate data for each decile of a population. When I try to 
plot the kernel density estimator (for sake of reference, you can define
 variable "test" to be 10, 20, 40, 50, 60, 70, 80, 90, 95, 99 and then 
try 

kdensity test, kernel(gauss) 

with various bandwidths), its peaks at each of the values are pointed 
rather than smooth. Yet if I try 

histogram test, bin(10) kdensity kdenopts(gauss) 

the density will appear much smoother, even for the same bandwidth and 
kernel. Comparing the results with R's "density(test, 
kernel=c("gaussian"), weights=NULL, window=kernel, n=100)", R's density 
also looks smooth (Stata's "kdensity test, kernel(gauss)" won't let me 
specify n(100) since the number of binned datapoints I have is 10). 
Ultimately I would like to use those 10 binned data points to plot the 
density across the whole population and sample from it so that I can 
infer some values for the person at the 26th percentile, the 27th 
percentile, etc.

Can Stata handle binned data like this?

Thank you.


      
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