Re: st: weight marker symbol fill size and color?

[David Airey <david.airey@Vanderbilt.Edu>]

.

Great! I get it now, of course. I also read an appreciated Nick Cox's  
notes to your post. Thanks for taking the time to show how to do this.

Cheers,

-Dave

On Aug 24, 2008, at 1:14 PM, Friedrich Huebler wrote:


> Dave,
>
> I asked a similar question on July 29.
>
> http://www.stata.com/statalist/archive/2008-07/msg01081.html
>
> A weighted scatter plot can be combined with markers in different
> colors as I learned from Stata tech support. I neglected to share the
> solution with the list so let me explain today how this can be done.
> The solution involves duplicating the observations and recoding the
> group variable in the duplicates. This way the weights are distributed
> across all groups.
>
> Say we want to take the census data from your example and identify the
> regions with different colors.
>
> . webuse census
> . scatter death medage [w=pop65p], msymbol(Oh) name(A)
> . twoway (scatter death medage if region==1 [w=pop65p], msymbol(Oh))
> (scatter death medage if region==2 [w=pop65p], msymbol(Oh)) (scatter
> death medage if region==3 [w=pop65p], msymbol(Oh)) (scatter death
> medage if region==4 [w=pop65p], msymbol(Oh)), name(B) legend(off)
>
> I turned off the legend so that it is more easy to see that the
> markers in graphs A and B have a different size. Next, expand the data
> and set the added observations to missing so that they won't appear in
> the graph.
>
> . expand 4
> . sort state region
> . replace death=. if mod(_n,4) > 0
>
> The next step is to recode the region in the added observations.
>
> . recode region (1=2) (2=3) (3=4) (4=1) if mod(_n,4) == 1
> . recode region (1=3) (2=4) (3=1) (4=2) if mod(_n,4) == 2
> . recode region (1=4) (2=1) (3=2) (4=3) if mod(_n,4) == 3
>
> Now we can draw a graph in which the markers have the same size as  
> in graph A.
>
> . twoway (scatter death medage if region==1 [w=pop65p], msymbol(Oh))
> (scatter death medage if region==2 [w=pop65p], msymbol(Oh)) (scatter
> death medage if region==3 [w=pop65p], msymbol(Oh)) (scatter death
> medage if region==4 [w=pop65p], msymbol(Oh)), name(C) legend(off)
>
> Below is the solution to the example from my original post of July 29.
>
> . clear all
> . input x y weight group
> 1 1 1 1
> 2 1 2 1
> 1 2 4 2
> 2 2 8 2
> end
> . scatter y x [w=weight], name(A)
> . twoway (scatter y x if group==1 [w=weight]) (scatter y x if group==2
> [w=weight]), name(B) legend(off)
> . expand 2
> . replace x = . if _n>(_N/2)
> . recode group (1=2) (2=1) if x==.
> . twoway (scatter y x if group==1 [w=weight]) (scatter y x if group==2
> [w=weight]), name(C) legend(off)
>
> Friedrich
>
> On Sun, Aug 24, 2008 at 11:42 AM, David Airey
> <david.airey@vanderbilt.edu> wrote:
>
> > At this page, we see how to change symbol size by using (analytic)  
> > weights:
> >
> > http://www.stata.com/support/faqs/graphics/gph/graphdocs/ 
> > scatter5.html
> >
> > e.g.,
> >
> > webuse census
> > scatter death medage [w=pop65p], msymbol(circle_hollow)
> >
> > Can we change both symbol size and color shading as in the R  
> > example below?
> >
> > -Dave
> >
> > ###------------------create the test data.frame
> > y = c(.4, 1, 2.15, 1.8, 2.7, 2.2, 1.3, .25, 1.1, .1)
> > x = c(.35, .4, .41, 1.4, 2.1, 2.25, 2.15, 2.2, 1.45, 1.3)
> > z = c(9, 7, 7.5, 7.3, 7, 7.1, 7.75, 9.5, 8, 10)
> > d = data.frame(x = x, y = y, z = z)
> >
> > d$col = gray(.5)
> > d$col[d$z>=9] = gray(.2)
> > d$col[d$z<7.5] = gray(.7)
> > #thikness = sqrt(d$y^2 + d$x^2)
> > thikness = abs(d$y) + abs(d$x)
> >
> > ###----------------simple, 2-D plot
> > plot(d$x, d$y, pch=19, cex=(d$z-min(d$z)/1.5), xlim = c(-1.5,4),  
> > ylim =
> > c(-2.5,5), col=d$col)
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