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  1. I would like to display point data values (indicating biomass at a point) but also to show the standard deviation value for each point. What would be the best method to do this in QGIS (I'm a basic user!). I do not have ±100 points. I am imagining a point with size = biomass and a buffer showing SDev, but I don't know how to do this.

  2. The next step would be to show the breakdown of values in each point by species (about 5 species biomass values making up the total biomass at each point). Would the best way be with a pie graph per point? And how to show each StDev?

I am using QGIS, Manifold and (less often) SAGA. Any suggestions welcome, many thanks

closed as unclear what you're asking by underdark Jul 31 '14 at 18:09

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • Welcome to gis.SE. What data do you have - format, elements, range? Can you show a small sample of that? What have you looked at already? What have you already tried? What worked for you? What didn't? What happened instead? The more information you can provide, the more likely we are to be able to help you. – BradHards Dec 4 '13 at 8:39
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In fact there are two different questions here: How should I represent this data, and how to do it technically. I'll focus only on the first here.

What is the source of the standard deviation? If it is due to the laboratory procedure, ... I would not show it on a map. It makes sense to do it if it represents spatial variation, eg you took different samples in a field.

I would not use a buffer to show standard deviation. Perhaps you can make points with a higher standard deviation more transparent? Or work with something akin to box and whisper plots.

If you want to show the breakdown per species I would no longer show the standard deviation. That is too much information to put on one graph. For the graph I would rather put barcharts than piecharts, you will be able to compare the values more easily.

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