[R] Density estimation: scale back for calendar time
David Winsemius
dwinsemius at comcast.net
Thu Mar 26 18:12:35 CET 2009
Pradeep Raje <raje.pradeep <at> gmail.com> writes:
>
> Thanks David for your response.I had done that.
But not shared it.
> Problem is not with the
> computations, but in the interpretation.
> Assume that x ordinates are 'time' [1:3472], and y are associated parameter
> values.
> Now density gives me 512/1024/2048 x-ordinates, of which some (7 to be
> precise) are negative. What do I make of the non-zero probability at
> **negative** times?
Obviously you are having problems with interpretation which is why I suggested
that you provide a worked example. Since you appear to be resisting that
suggestion, let's talk about hypotheticals. Two results of a density
estimation will be density(dat)$x and density(dat)$y. The first of these is not
a probability and could be negative in any instances where negative numbers
were in the domain of the dat object. And it might be negative in situations
with postive values where an estimation extended slightly beyond the original
dataset. It is the y values that are necessarily positive.
The idea that dates associated with a numerical object could be used to label a
density plot seems strange. The process of density estimation would scrample
the order of the original data so that the densities could be calculated. In a
sense the y-axis of the original object will become the new x-axis of the
density object. There would be no way to restore that "date" order. It had been
my hope that a request for an example would make that more clear. Back to you.
--
David Winsemius
>
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