[mapserver-users] Get MAP file CLASSes with no data - empty

[Armin Burger]

Michal

I hope I understood your question correctly...:

the following code returns all class indexes for the provided layer and 
full map extent that appear in the data.

$me = $map->extent;
$layer->open();
$status = $layer->whichShapes($me);
$classWithData = array();
while ($shape = $layer->nextShape()) {
     $shpIdx = $shape->index;
     $clsIdx = $layer->getClassIndex($shape);
     if (!in_array($clsIdx, $classWithData) && $clsIdx >= 0) {
         $classWithData[] = $clsIdx;
     }
}
$layer->close();

You could use this to get first all classes *with* data and then 
calculate the difference of this array with the array of total classes. 
The resulting array should contain the classes that are *not represented 
in the data* , like

$allClasses = range(0, $layer->numclasses-1);
$noDataList = array_diff($allClasses, $classWithData);
print_r($noDataList);


Note however that this works like listed above only for layers that have 
the same projection as the map. If both projections are different then 
the call of "$layer->nextShape()" causes a segmentation fault (in both 
MS 5.6 and 6). In this case you need to re-project the layer beforehand 
to the projection of the map, then it should work.

Armin


On 17/12/2011 22:35, Michal Seidl wrote:
> I would like to get in PHP/Python environment the list of CLASSes which do
> not target any data. The situation is like this.
>
> 1) I am interested only in vector data
> 2) I have mapfile and running mapserver
> 3) There is LAYER with many CLASSes which are defined by EXPRESSION in
> mapfile
>
> Any suggestion how get classes with no data?
>
> Thanks Michal
>
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> View this message in context: http://osgeo-org.1803224.n2.nabble.com/Get-MAP-file-CLASSes-with-no-data-empty-tp7104765p7104765.html
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