Methods for constructing blurs, as used in the blur argument to
geom_blur_dots() or stat_mcse_dots().
Supports automatic partial function application.
Arguments
- x
numeric vector of positive distances from the center of the dot (assumed to be 0) to evaluate blur function at.
- r
radius of the dot that is being blurred.
- sd
standard deviation of the dot that is being blurred.
- .width
for
blur_interval(), a probability giving the width of the interval.
Value
A vector of length x giving the opacity of the radial gradient representing
the dot at each x value.
Details
These functions are passed x, r, and sd when geom_blur_dots()
draws in order to create a radial gradient representing each dot in the
dotplot. They return values between 0 and 1 giving the opacity of the
dot at each value of x.
blur_gaussian() creates a dot with radius r that has a Gaussian blur with
standard deviation sd applied to it. It does this by calculating
\(\alpha(x; r, \sigma)\), the opacity at distance \(x\) from the center
of a dot with radius \(r\) that has had a Gaussian blur with standard
deviation \(\sigma\) = sd applied to it:
$$ \alpha(x; r, \sigma) = \Phi \left(\frac{x + r}{\sigma} \right) - \Phi \left(\frac{x - r}{\sigma} \right) $$
blur_interval() creates an interval-type representation around the
dot at 50% opacity, where the interval is a Gaussian quantile interval with
mass equal to .width and standard deviation sd.
See also
geom_blur_dots() and stat_mcse_dots() for geometries making use of
blurs.