[mapserver-dev] general problem with bar charts

[thomas bonfort]

hi
from the charting howto on the documentation site
(http://mapserver.gis.umn.edu/docs/howto/dynamic-charting), you've got
two directives that should meet your needs:
PROCESSING "CHART_BAR_MINVAL= ... "
PROCESSING "CHART_BAR_MAXVAL= ... "

please keep in touch if that doesn't solve your problem

regards,
thomas

On Thu, Feb 21, 2008 at 5:58 PM, Karsten Hoffmann
<khoffmann at igf.uni-osnabrueck.de> wrote:
>
>
>
>
> Hi developers,
>
>
>
> I'm not sure if somebody has already recognized the following problem.
>
> I found out that the bar charts in mapserver 5.0 are not really useful for
> thematic mapping. Bar charts of different features in a map are not
> comparable with each other because the maximum values in each chart have the
> same size (height).
>
>
>
> For example I have two features with the following attributes:
>
> Feature A: 1000, 500, 200
>
> Feature B: 2000, 1000, 400
>
>
>
> Both features have exactly the same bar chart in the same size (height)
> which I have defined for example with PROCESSING "CHART_SIZE=30 40". This
> gives a wrong map and a wrong impression to the map reader. The height of
> the bars of Feature A should only be the half of the bars heights of Feature
> B.
>
>
>
> My impression is that the maximum value of the given attributes for one
> feature is always drawn with the defined height. All other values in this
> chart are drawn relative to this height.
>
>
>
> It would be better to define a global height for a value (for example 30
> pixels is equivalent to 2000). All bars of all charts should then be drawn
> relative to this definition.
>
>
>
> Another very useful function for thematic mapping would be the possibility
> to vary the size (diameter) of pie charts relative to an attribute or the
> sum of the values which are used for drawing the pie slices.
>
> But I found out that this is already in the works and will hopefully come
> with version 5.2 (see http://trac.osgeo.org/mapserver/ticket/2136).
>
>
>
> Best regards,
>
> Karsten Hoffmann
>
> --
>
> Dipl.-Geogr. Karsten Hoffmann
>
> Institut für Geoinformatik und Fernerkundung (IGF)
>
> Universität Osnabrück
>
> Seminarstr. 19 a/b
>
> 49069 Osnabrück
>
>
>
> Raum: 02/106
>
> Tel.: +49 541 969-4233
>
> Fax:  +49 541 969-4061
>
> E-Mail: khoffmann at igf.uni-osnabrueck.de
>
> Web:  www.igf.uni-osnabrueck.de
>
>
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