On Thu, 1 Oct 2009, kayj wrote:
> I am having difficulties interpreting a cdplot, I have a binary variable y
> that I want to cdplot against a continuous variable x,below is the R
command
>
> cdplot(y~x, data=mydata)
>
> you get a plot with a dark shaded area and a light shaded area. what do
> these areas mean? and how to interpret the plot?
>
> you help is greatly appreciated
See ?cdplot. It's a display that graphs (an approximation of) P(y | x)
against x. The areas above and below the line are simply shaded in
different levels of gray.
To obtain P(y | x), the idea is to use
f(y | x) = f(x | y) * f(x)/f(y)
where for f(x) and f(x | y) are obtained by (unconditional and
conditional, respectively) kernel density smoothers from density().
f(y) is simply the unconditional proportion of the category y.
hth,
Z
>
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