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This might be a stupid question and I apologize if so. I have count data for different trails. They are points and I would like to make an average of those counts for each trail so that each trail has a count value. I don't know if I am being clear... Later on I would like to have a probability of encoutering the different species that were counted along those trails depending on the average counts. I am fairly new to GIS and I have no idea which tool I could use to do that... I was thinking of interpolation but I want to model the trails only, not the whole layer. I hope I have been clear enough and you will not mind my ignorance, Thank you,

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It is difficult to see how one could reasonably hope to estimate a probability of an encounter from counts alone, so I presume you have more information than you have outlined so far. Please edit your question to be more specific about how your data were collected and measured. How were the points determined? What do the counts count? How is the "species" information determined and how is that related to the counts? Posting a small example of your dataset might help clarify the question, too. –  whuber Jun 26 '13 at 20:40
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It is wide question. First this doesn't have to be necessary spatial task. You can look at it as sets of values for different trails and count average/mean/min/max for values in every trail (whatever the position of points in trail is)...

If you have points, you must somehow specify which points belongs to which trails:

a) separate file for every trail

b) in the table have column as "trail_identificator"

Technically all you need is software able to work with table data like Open Office Calc. You can create table with columns like: point_id, x, y, trail_identificator, observed_value, mean_value_for_trail, sum_for_trail etc.

GIS software (like QGIS) allows you ta save/export or load/import table data so after your calculations you can spatially visualize the information as colored points. Or you can have/create trails as lines and add this final values to table connected to these lines and color/scale line symbol based on your calculated value.

I am not going to explain how to automatically convert points to lines or how to visualize variable probability value along the line because that is way more complicated and I guess it is not needed in this case.

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Thanks all for your answers. I have decided to keep it a little simplier and I will use the method described by Miro. :) –  Elena Spark Jun 29 '13 at 21:40
    
Elena could you please in that case click on accept (check symbol) to make this question officially answered :) Thank you. –  Miro Jul 2 '13 at 4:59
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