dynamic symbols, eg bar graphs or pie charts

[thomas bonfort]

Steve: actually tim's implementation creates a new point layer , dynamically
creates images for each pie chart, and associates each of the points with
its corresponding image. The overhead is quite noticeable for more than a
bunch of pies to be generated.

Steve and Daniel: the url type symbol does seem promising feature-wise. but
once again the overhead of network request and probably two intermediate
files (one for owt, one for MS) seems quite important.

tb

On 6/9/06, Steve Lime <Steve.Lime at dnr.state.mn.us> wrote:
>
> Thomas: I hadn't looked at Tim's implementation but "thought" he was using
> the pie chart demo I had put together. That is a native implementation. It
> would be helped by a startangle parameter which would make data setup more
> intuitive. (this is what got RFC percolating in my head)
>
> As for bar charts, I was thinking about that too. With attribute bindings
> for size
> this is almost doable with styles now. That is, each style could represent
> a bar.
> with offsets applied to form the chart. The missing piece is that
> MapServer
> locks the symbol aspect ratio for symbol scaling and/or allows only 1 size
> value.
> One solution would be to allow size to set 2 values- width and height.
> With the second
> being optional. That would be a painful modification I think. A better
> option might
> be to use with already present WIDTH parameter for markers, so the width
> would
> define the marker width (if present) and size would represent height
> (which is what
> it really represents anyway). That would not be a difficult modification.
>
> That would allow relatively simple charting, but for use as a marker
> that's really all
> you could do.
>
> One last idea would be to allow the use of a URL to define a marker. That
> would allow
> remote images to be used, but would also allow the use of external
> programs to do things
> like charting (think OWTCHART) or custom markers. Allow that URL to be a
> template and
> take item substitutions:
>
>   SYMBOL 'http://someserver.com/cgi-bin/charting?data=[X1],[X2],[x3],[x4]'
>
> and you really have something interesting... With libcurl this might no be
> too bad.
>
> Steve
>
> >>> thomas bonfort <thomas.bonfort at GMAIL.COM> 06/09/06 7:37 AM >>>
> hi all,
> I'd be interrested in having/adding  pie charts or bar graphs to
> mapserver,
> in order to output thematic maps...
> I've experimented with Tim Schaub's hack for pie charts which is very nice
> but a bit too cumbersome for large datasets, and was wondering if this
> could
> be natively done by mapserver...
> Could this fit in the symbology methods of MS, by defining a new type of
> "dynamic symbol" which would resemble a pixmap symbol except that the
> pixmap
> is generated from the input data?
> I'd be willing to give a shot at this if you folks think this is
> worthwile.
> cheers,
> tb
>
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