[R] density() returns a density function that does not add up to 1

A.J. Rossini rossini at blindglobe.net
Fri Aug 30 22:09:03 CEST 2002

>>>>> "jonathan" == Jonathan Li <jonqli at labs.agilent.com> writes:

    jonathan> Dear R users,
    jonathan> I ran into this curious problem:

    >> d <- rnorm(100)
    >> d.density <- density(d)
    >> sum( d.density$x * d.density$y)
    jonathan> [1] 2.517502

whoops, you probably want something like: 

> sum( diff(d.density$x) * d.density$y)
[1] 1.000950

instead, for a crude integration (and yes, it throws a warning).

A.J. Rossini				Rsrch. Asst. Prof. of Biostatistics
U. of Washington Biostatistics		rossini at u.washington.edu	
FHCRC/SCHARP/HIV Vaccine Trials Net	rossini at scharp.org
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