On 6/09/2008, at 8:32 AM, pragmatic wrote:
Hello!
Please, anybody help me.
Can I calculate area of density was created by:
D <- density(x)
In other words I want to know area under curve 'plot(D)'
and It's good to calculate area before and after 0 separately.
(1) You could use splinefun()
foo <- splinefun(D$x,D$y)
integrate(foo,min(D$x),0)
integrate(foo,0,max(D$x))
or you could use simp() from
http://finzi.psych.upenn.edu/R/Rhelp02a/archive/134918.html
with(D,simp(y=y[x<0],x=x[x<0]))
with(D,simp(y=y[x>0],x=x[x>0]))
You'll get different answers, neither of which is ``correct''.
cheers,
Rolf Turner
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