[R] Gray level mosaic plot with shading_Friendly

[Achim Zeileis]

On Tue, 6 Jul 2010, Michael Friendly wrote:

> Michael Kubovy wrote:
>> Suppose we start with
>> 
>> data("Titanic")
>> mosaic(Titanic, shade = TRUE)
>> 
>> How do I combine the dashed box contours of shading_Friendly to indicate 
>> negative residuals, with three levels of gray: dark for abs(Pearson Resid) 
>> > 4, lighter for 4 > abs(Pearson Resid) > 2, and lightest for bs(Pearson 
>> Resid) < 2 ?
>> 
>
> Do you mean [1] you want to plot positive residuals in color and negative in 
> gray scale?
> Or [2] to fold + and - residuals by shading all according to abs(resid), and
> distinguishing + from - by the dashed box outlines?
>
> In fact, I designed this coding scheme so that mosaic plots in color (with my 
> blue - white - red scheme) would approximately do exactly what
> you might want under [2], when rendered in B/W, since the fully saturated red 
> and blue are close in  darkness in B/W.

And shading_hcl() has been written to do exactly what you want under [2]. 
While it is hard to come up with colors of different hues in HSV or HLS 
space that have the same brightness (aka lightness/luminance) and the same
colorfulness (aka chroma), this is easy in HCL.

> Try
> mosaic(Titanic, gp=shading_Friendly)
> save as a jpg/png and try converting to B/W with an image program and see if 
> this is good enough.

mosaic(Titanic, shade = TRUE)

is the same as

mosaic(Titanic, gp = shading_hcl)

which you can then modify to have different line types

mosaic(Titanic, gp = shading_hcl, gp_args = list(lty = 1:2))

If you print that on a grayscale printer you will see the same plot 
without any chroma, i.e.,

mosaic(Titanic, gp = shading_hcl, gp_args = list(lty = 1:2, c = 0))

The shading_hcl() function is introduced in Zeileis et al. (2007, JCGS), 
see ?shading_hcl, which provides more detailed references to HCL colors 
etc.

Best,
Z

> Alternatively, write your own, shading_Kubovy, modeled on
>
> shading_Friendly <-
> function (observed = NULL, residuals = NULL, expected = NULL,
>    df = NULL, h = c(2/3, 0), lty = 1:2, interpolate = c(2, 4),
>    eps = 0.01, line_col = "black", ...)
> {
>    shading_hsv(observed = NULL, residuals = NULL, expected = NULL,
>        df = NULL, h = h, v = 1, lty = lty, interpolate = interpolate,
>        eps = eps, line_col = line_col, p.value = NA, ...)
> }
> <environment: namespace:vcd>
> attr(,"class")
> [1] "grapcon_generator"
>
> In the defaults, lty=1:2 is what distinguishes + and - for outline line type
>
> hope this helps,
> -Michael
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>