Latest Contributions by AdamBorczyk

Since selections is defaultdict(dict), I think the error can appear only because there is no row[0], row[1] or row[2]. Please try to print it and see it you get correct results from cursor. ... View more

This is my code, I hope it helps you James Crandall‌         import arcpy     from collections import defaultdict     vector = 'yourShapefile.shp'     # glac_id is my area ID, FID is the very first column in ArcMap attribute table and I calculate length of the shape on the fly     fields = ["glac_id", "FID", "SHAPE@LENGTH"]     selections = defaultdict(dict)     top3 = defaultdict(list)     with arcpy.da.SearchCursor(vector, fields) as cursor:         for row in cursor:             selections[row[0]][row[1]] = row[2]     for i in selections.keys():         # I take 3 last items (3 biggest) or sorted list of values. I could also reverse it and get 3 first ones.         top3[i] = sorted(selections[i], key=selections[i].get)[-3:]‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ The if I print top3, it will give me: defaultdict(<type 'list'>, {u'G012161E78870N': [41, 46, 47], u'G011895E78886N': [5, 3, 18], u'G012039E78878N': [44, 42, 17]})‍ which are FIDs of 3 longest lines per area. Now all you have to do is extract lines by ID from original file (or do whatever you want). ... View more

Thank you everyone for your help. I missed the part of docs saying that ORDER BY won't work with shapefiles. Fortunately a where clause works, so I can get my output in a little bit longer way. I just have to iterate over entire cursor and find max (or top 3) from the results. ... View more

Thank you for your code. I was too fast though. It appears that your and my code correctly use"where" clause, but totally omit "sql_clause". With the code you supplied, when I iterate over "result" (removing .next() beforehand) I get all records belonging to my area ID, but unsorted. Maybe sql_clause needs some more parameters which aren't documented that well? ... View more

This one works! Partly though. I can get correct result if I specify where_clause for a given area, but not a general highest result. When I don't know exact area IDs, this method will be hard to use. Without specifying WHERE, the sql_clause does not give any effect. ... View more

This is correct and it would be the next step I did, but I cannot even get to this point, because ArcPy doesn't honour any ORDER BY clause. What more, trying to put `'glac_id = "G012039E78878N"'` as `WHERE` clause doesn't modify results at all either. ... View more

Thanks Joshua Bixby and Randy Burton, I know how TOP and ORDER BY should work, but the point here is that none of example queries in `sql_clause` work, I couldn't get any ORDER BY or GROUP BY to work, or anything else. This is the code I tried right now: import arcpy arcpy.env.overwriteOutput=True testVector = r"C:\Users\adam\Desktop\testarcpy\cont_int.shp" fields = ["glac_id", "length"] sql = (None, 'ORDER BY length DESC') # One method (get ordered list) with arcpy.da.SearchCursor(testVector, fields, None, None, False, sql) as cursor:      for r in cursor:         print r # Other method (just give me longest one) OID = arcpy.da.SearchCursor(testVector, fields, sql_clause = sql).next() print OID‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ With above I always get unsorted values from the table. Even if 'length' was a string (which is not, it's a float), it is not ordered in any way, I get rows in the same order as they are in attribute table in ArcMap. There are no duplicate columns in the file obviously, no Nulls, nothing special really. I also tried ordering by SHAPE@LENGTH with no luck (same result again). Path to file is correct (I've just triple-checked it), column names are fine. I also tried with a test WHERE clause: 'length > 100.0' with no luck again. Very same results. I hoped this was a simple syntax error I just couldn't spot, but it looks like a bigger issue now. ... View more

Thanks. I am iterating over a simple shapefile, and if I stop using TOP and change clause to eg. `sql = (None, 'ORDER BY "length" ')`, I still get every record. ... View more

Thank you, that made it. Afterwards I only had to select by attributes (where X/Y > Z) and do some Joins and Spatial Joins to get a clean attribute table with glacier name and the value. In my case, where more than one "ranges" were selected I also also summarized them by original FID, so I got an average of all selected boundaries (ranges). ... View more

Hi, thanks. This doesn't have any effect on pixel depth though. The advantage is only that you don't need to run separate Clip Raster tool (which takes a long time) - of course in case you actually need any clip. ... View more

Thank you Dan and Günter. Although I was looking for the smoothing function from Image Analysis, it was faster to implement the Filter tool with low pass filtering and the result was similar, so that was sufficient for me. ... View more

You're right, but the Pricipal Components just doesn't honour this Environment setting. ... View more