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I've got a data set of people movements within my municipality. (between points of places)

I've managed it with the plugin for QGIS 'time manager'. Over time people come and go, and based on a count of movements of a specific point at a specific time (time manager), i want to let my point symbol grow.

Is this possible with QGIS rule based symbol?

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Could you please explain your the data structure? Do you have a single point feature with different values (attribute) over time, or do you have separate point features for different dates? –  Alexandre Neto Jan 9 '13 at 14:05
    
I have separate point features for different dates. –  Taeke van der Laan Jan 9 '13 at 22:41
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The only solution I know of so far is to add a size attribute to the features you want to grow and calculate the growth using e.g. Field Calculator. Then you can set up Time Manager and - in the layer style - add the size scale field in the style's advanced settings.

Note: There is no size scale field in rule based symbology. Change to a different one.

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I had also the thought of using a calculate function within qgis. But when you set up a new field, then you will only update that field at a specific time. It is static, not dynamic over time. Or am I wrong? –  Taeke van der Laan Jan 10 '13 at 12:38
    
Yes the field is static. You said that you have separate point features for different dates. So at every date you can set a different size value. –  underdark Jan 10 '13 at 12:47
    
Yes of cource, I can update my table whit a count for that specific time. So it doesn't have to be dynamic.....thanks for the eye opener –  Taeke van der Laan Jan 10 '13 at 13:01
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Also, If you want to calculate the "grow variable" automatically, without the need to use calculate field every time you add a new point, you can put your data in spatialite or postgis, and add the layer in to your project through a spatial view. –  Alexandre Neto Jan 11 '13 at 11:25
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