Nov 14, 2011 at 2:13 AM
Edited Nov 14, 2011 at 2:22 AM
My current project is to map selected statistics from the February 2012 Chicago municipal elections.
The is to map not only raw data (how many votes were cast in this precinct, how many were cast for each candidate, etc) but also to map complex data (how big a lead did the winner have, what percentage of the votes did he garner, etc).
The map will have one layer for each type of statistic, and each layer will colorize one statistic's value for each of the 2574 precincts in Chicago.
As far as I can tell, MapWindow currently requires that I add 2574 values to the attribute table for each new statistic that I want to display. This will entail a large and ever-expanding attribute table, holding more and more values as people request
more and more statistics. Or else it will require that each new statistical layer have its own,new attribute table, offering is single pertinent attribute.
But help may be in sight.
One nice feature of MapWindow 4.8.6 is that labels need not mirror exactly one attribute, but can be computed from a formula referencing several attributes.
If this feature can be slightly extended, it would be a great boon for my project.
The desired extension is this: Allow a layer's labels to serve as "virtual attributes"--as virtual members of the layer's attribute table.
This would allow complex statistic to be computed on-the-fly from raw data in the attribute table, and then, like any other attribute, to be used in colorizing the map's terrain.
This holds great advantages for the map administrator:
* A label formula takes up orders-of-magnitude less disk space than the corresponding individual attribute-table entries.
* Because the label formula is not stored in the attribute table, the attribute table itself has no need to be modified. As a result,
** One and the same attribute table can be employed for all the statistical layers. This saves much disk space.
** The administrator has no need to modify or create an attribute table for each new statistic. This saves the administrator much time.
** The administrator has fewer attribute tables to maintain. This, too, saves the administrator much time.
So, is it possible to extend the label feature in this way?