[Groff] RE: Venn Diagram in Pic?

[andlabs]

Do they still make ideal? If so, it might help. ideal draws absolute pictures
using primitives.


Ted.Harding wrote:
> 
> On 12-Sep-07 14:12:46, Webb Roberts wrote:
>> What is the easiest way to get a Venn diagram in Groff?  Pic doesn't
>> seem to like overlapping shapes.
>> 
>> Thanks,
>> Webb
> 
> It's not clear what you mean by "Pic doesn't like overlapping shapes".
> 
> There is no problem with drawing boundaries for the one-factor regions.
> E.g. if you have 3 factors A, B and C you can draw a region for A, a
> region for B overlapping the A region, and a third region for C
> overlapping all three sub-regions within the first two.
> 
> This then defines 8 sub-regions: abc, Abc, aBc, abC, ABc, AbC, aBC
> and ABC, say (where "abc" is outside all the regions you drew),
> which you can label with corresponding text.
> 
> However, if you were to try to fill the three regions say with colour
> or shades of grey as you draw them, then the last one drawn
> (say C) will be entirely the colour or fill that you drew it
> with, and this will blot out the subregions for the other
> categories -- i.e. abC, AbC, aBC and ABC will all look the same.
> Not that irregular shapes can be readily filled in pic anyway.
> 
> The real problem with Venn diagrams arises when you have more
> than a few (say 5) factors. It is very difficult indeed (though
> not impossible) to invent 5 simply-connected regions each of
> which overlaps the others in all possible combinations -- 4 is
> bad enough!
> 
> Best wishes,
> Ted.
> 
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> E-Mail: (Ted Harding) <address@hidden>
> Fax-to-email: +44 (0)870 094 0861
> Date: 12-Sep-07                                       Time: 15:44:53
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> 
> 

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