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does anyone know of a way to find the standard deviation of an attribute lying within any given polygon? The plugin dialog "Join Attributes by Location" gives only the options Mean, Min, Max, and Sum. Alternative ways of getting the results are welcome too, of course.

I'm using Quantum GIS 1.6.0.

Thank you!

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I have the same problem like Quincy, I created a buffers and I would like to calculate the StDev and CV for each buffer but with the "Join Attributes by Location" gives only the options Mean, Min, Max, and Sum. However I don't know any python. Quincy (or some one else), would you mind to send me the python script you used for? Thank you soo much! PB –  Pilar Berenguer Aug 21 at 13:50

1 Answer 1

up vote 9 down vote accepted

"Statist" plugin calculates StDev. It has a "use only selected features option".

You'll need to use "Select by location" first to select the features within your polygon-of-interest. Then run Statist.

enter image description here

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Thank you for your answer! It's really helpful but not quite what I'm looking for. –  Quincy Jun 2 '11 at 18:24
    
I have over 500 polygons and would like to calculate the StDev of an attribute in all 500+ polygons.. is there an easier way to do this? –  Quincy Jun 2 '11 at 18:26
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Oh I see. Sounds like it would be easiest to add that option to "Join Attributes by Location". If you know some python it shouldn't be much work. –  underdark Jun 2 '11 at 18:39
    
Thank you! I did exactly that. Stack exchange won't let me confirm the answer because I created a new account. Thanks still! –  Quincy Jun 4 '11 at 23:36
    
@Quincy You have only one account on GIS.SE linked to your e-mail address. You should be able to accept this answer. –  whuber Jun 5 '11 at 22:27

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