[GRASS-user] Precipitation color table?

[Luigi Ponti]

Hamish wrote:
> Luigi Ponti wrote:
>   
> [...]
>> However, when you have a continuously varying color bar in the map,
>> you will have label numbers next to the bar and you will try to
>> associate the bar color next to the label value with a color in the
>> map. The argument Borland & Taylor (2007) make is that if each label
>> of the color bar is located between two constant color bands in the
>> bar, you will have that value easily located in the map along the
>> boundary between the two contiguous areas of constant color. What do
>> you think about this?
>>     
>
> So they argue that (filled) contour lines are better than continuous
> rainbow legend. Well, why not draw contour lines over the top of a
> continuous rainbow then? It is a false dichotomy, as you can do both
> together. My feeling is that there is more room for danger with
> contour lines than with the reader squinting to see what orangish-
> yellow means. Contour lines are dangerous because they state loudly
> where a transition is, regardless of if the data has that confidence or
> not. It is like the difference between politicial speak and scientist
> speak in a way, one gives black and white options, the other gives some
> probability that a theory is correct.
>   

OK -- I got the point and that's good because I don't have to change the 
way I am doing things. Plus you provided good arguments to support it.

>   
>> I have no bias given my very limited experience on the matter -- just 
>> trying to make an informed decision. Thanks again for discussing this 
>> and sorry if this is way off topic for the list (please advice).
>>     
>
> I veer way offtopic as well, and again it reminds me about the next book
> I need to borrow from the library (www.edwardtufte.com).
>   

Yes: it's highly cited by both supporters and enemies of constant color 
bands.

> To claw back on topic I will mention that you can have a rainbow
> colorscale with crossing band lines in ps.map: give the "tickbar"
> instruction to the colortable command. (then create and overlay contours
> at those levels)
>   

That's something that can turn useful, thanks!

[...]
>>> The statistical equivalent is to slowly vary the number
>>> bins in a histogram while the peaks seemingly double and halve.
>>>       
>> Yes, you lose information that way.
>>     
>
> And worse, it is very easy to do so without noticing that you've done it.
>   

Thank you for a very interesting thread -- it's nice to veer off-topic 
every now and then.

Luigi
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/grass-user/attachments/20080925/b40eaf80/attachment.html