dhis2-users team mailing list archive

[Bram Piot <bram.piot@xxxxxxxxx>]

Hi Bob,

I don't think there's one single rule that will fit all when it comes to
choosing your symbols or colours for a thematic map depicting numeric
values. There's nothing wrong with say a red/yellow/green colour scheme if
you are showing for example reporting rates, where low (red) = bad and high
(green) = good. If I were to map out HIV prevalence, then I may go from
green (low values) to red (high prevalence). More "neutral" variables such
as population density are usually better off with a graduated scheme from
light to dark, e.g. pale to dark brown.

Maybe the only basic rules are that there should be some logic in the
choice of colour ramps, and to keep it simple (don't overload your map,
don't use 15 different classes each with a different colour when you only
have 20 districts!). I must agree that the current colour scheme for ANC1
and ANC2 coverage by chiefdom in the demo site can definitely be improved:
too many colours that are not in a logical order. Your diarrhea map looks
better, though it would be even better if you changed the classification
type to "equal counts" rather than "equal intervals".

Agree with what has been requested recently by Knut: option to display
polygon data (e.g district) by symbol, not just colour, and include more
symbols because currently it's rather limited. Especially for categorical
values the legend behaviour could be greatly improved. Bar/Pie charts as
symbols on the map would be cool but not a priority as there are more
suitable tools for that.

bram


On 20 February 2014 17:27, Bob Jolliffe <bobjolliffe@xxxxxxxxx> wrote:

> Hi
>
> I am no expert here, but I was talking last week with someone who had just
> been on a GIS course.  She made the interesting observation that when you
> are displaying numerical data as shaded regions on a map, you should not
> mix primary colours in the same gradated scale because what you end up with
> is sort of rubic cube kaleidoscope of colour rather than a clear gradation
> of values.
>
> If that is good advice then I think our demo site could be improved as
> presently it seems like a good example of bad practice, where we have mixed
> red, green and blue with joyful and cheerful abandon :-)
>
> I had a go to change the Diarrhoea map on the dashboard at
> http://apps.dhis2.org/dev/dhis-web-dashboard-integration/index.action and
> I think it is true that it conveys the data better than the extreme
> multi-coloured ones around it.  Even if the distribution of data between
> bands is not so interesting.  Anyone agree or disagree? (the data will only
> be there for a short while longer)
>
> If there is a best practice to be had here regarding colour selection I
> guess we should promote it, particularly with default offerings so that
> people have to be quite deliberate in order to go astray.
>
> Bob
>
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