Latest Contributions by DavidMedeiros

I think Featue To Line tool (ArcInfo license) breaks lines where they intersect or share a segment. Each output line carries the FIDs of all the sharing lines, or -1 for no sharing line with an input fc. You would need to add a field to the result and calculate the count of FIDs that are not -1 by an expression. Again, thank you. That worked as well. I never look to these tools as geometry tools but should probably know more about them (meaning the "feature to..." tools). I did have to massage the table after words. There may be a more automated way of doing this but I simply used a series of selections and field calculations to change the values in each of my 6 FID fields to either a 1 or 0 then used the field calc to sum those into a new column. Now looking at how to create an accumulation of values for each segment based on its location in the river network and the values of all downstream segments. This is going to be a lot more involved and complex so I'll just post a new topic. ... View more

Thank you for letting me know. You are welcome. I am glad it worked for you.  🙂 I have a new similar question if you're interested? I have 6 line feature classes, each one is of a particular fish species distribution in the Oregon river system. Each feature class contains only the line features where that species is present, some lines overlap between the 6 layers, some don't. I want to output a new layer that is a collection of all the river segments from the 6 layers where each segment contains the count of the species in that segment and the unique species names. Union (Analysis) looks like it does what I want but this is a polygon only tool. I think I could do this thru a series of spatial joins to a master hydrology layer but a one time merging of the 6 line layers would work better. Any ideas how I could best tackle this analysis? ... View more

When you run Spatial Join, you can specify a Merge Rule - Count on a field. In your case, for each line you can get a count of matched dam features (FIDs). Sorry for the late reply, thank you Dan, yes this worked great. ... View more

Well it turns out I have two variations on this problem that need to be addressed; one involves getting single overlap polygons that inherit the unique species ID from the input polygons (as already described above). The other version is to get overlap polygons that sum the values of one field from the input polygons, and I think I managed to do this today. Here's the work flow: add original polygon layer [union] polygons, keeping all attributes (stacks identical polygons) open table to union layer add 3 new fields; x_coord, y_coord & xy_id calculate geometry for x & y coord fields create UID by concatenating coordinates into the xy_id field [dissolve] union layer on xy_id; use a sum statistic operation during dissolve to sum selected values of stacked polygons (in this case the "count" field) output layer polygons are single non stacked polygons of the overlap and non overlap areas with a count sum from all identical polygons in its stack Does that seem right? It worked on my very basic sample file. For the other issue, retaining unique species info and concatenating into one field for the dissolved stack I found the link below. Will try later, not sure how complex the species data is (still have not interviewed the student). http://forums.arcgis.com/threads/12637-Union-intersect-Concatenate ... View more

The dissolve will need to be run so that you are left with a single polygon for each overlap, not stacked polygons. This is only possible if a UID has been generated for the overlapping polygons. One way to do this, is to generate a pt from the Unioned overlay, and dissolve those points based on their X,Y coordinates (matching UIDs in this case) and then create a new field and populate a UID using any method you are familiar with. in field calculator: "ABC" & "-" & [FID] + 1 or whatever Then perform a spatial join to transfer attributes from the centroid pt, to the unioned polygon. Your GDB should then be ready for the relate. That archived post does leave out a lot of intermediate steps because the assumption is that the user has some basic working knowledge of ArcGIS as seen in the initial post. Its assumed you know how to eliminate the stacked polygons (identical spatially) into a single polygon. And also how to populate a field to concatenate the values in the related table. In the last post of the archived forum, download the Zipped mxd and gdb to explore how it was done (hint: explore the GDB when in ArcCatalog to observe the relates, tables, structure, etc...) Ok, that work flow is making some sense to me now. Thank you. Work copy of Arc does not have the full Data Management tool box installed so can't generate points from poly here. But will give the process a try at the Library tomorrow. ... View more

How do you merge 2 identical polygons and combine / concatenate attributes use a relate after a dissolve (before dissolve, attribute table is exported for the relate later). I may not be understanding the example clearly but the Dissolve aggregates my separate polygons (if done after a Union) or simply does nothing when applied to my initial sample file and run on the Species field. Seems like such a simple action, to merge identical stacked polygons, or at least concatenate the species data into the top polygon in the stack. One key piece of info I am still missing (until I interview the student myself) is the exact need for this data. I'm assuming a simple need to visualize the overlap extents. ... View more

I ran some test data this morning at work, similar looking to the image attached in the first post here. Neither result is what I'm after. Intersect gives only the overlap areas as output and ignores the remainder of the polygon where there is no overlap. Overlaps are stacked and separate (as Mathew mentioned above). Union gave me separate polygons for each overlap as well as the non overlap remainders. So where poly A, B and C overlap there are 3 identical stacked polygons clipped to the overlap area: A, B and C. What I'm after is a tool or sequence of tools that will give me a single polygon at each overlap that contains the attribute info for all overlap areas in that stack. So at the A,B & C overlap I would get a single clipped poly that was now ABC. I get the basic functions of intersect and union, but I need to go one step further and am not sure what approach to take. ... View more

start with the online help http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/An_overview_of_the_Overlay_toolset/000800000009000000/ Yes, that is where I started Dan. And my reading is that either Union or Intersect are the correct tools for me to use here. I originally thought Intersect would not handle more than two polys in an overlap but read in the description that it can do any number of overlaps. My concern is how what happens when you intersect a large number of polygons with varying levels of overlaps within the same feature dataset (all species). What will the output table look like, will I get multiples of the species attribute field for each species at the overlap location. I just need to run the data to figure this out... was just looking for some dialogue on what tool to use while I'm at home thinking about this. ... View more

what did you get running the various options on your sample file? I haven't had a chance to try these in Arc yet, I was given the question just before leaving the library today and don't have Arc at home. I'll do some experimentation tomorrow but thought I would do some research outside of Arc in the mean time. ... View more

Ok, I think I got it. Here's the script: Script: # split table script #add field step import arcpy from arcpy import env inputTable = arcpy.GetParameterAsText(0) arcpy.AddMessage ("input " + inputTable) #list fields (stops duplicate add fields) theFieldList = arcpy.ListFields (inputTable, "Type") arcpy.AddMessage ("the count" + str(len(theFieldList))) #following exectues the add field if len(theFieldList) == 0:     arcpy.AddField_management(inputTable, "Type", "TEXT")     else:     arcpy.AddMessage ("Field Exists")     #split field loop rows = arcpy.UpdateCursor (inputTable)  #gets all vlaues for table for row in rows:  #loops through vlaues and updates new field basedon last word of orig field     row.Type = row.Dest.split(" ")[-1] if " " in row.Dest else ""     rows.updateRow(row) del row del rows resulting table has a new field "Type" with the second word from the "dest" row copied over. If no second word nothing is copied over. Thanks for the help all! ... View more

Ahh, I mistook last value for last whole word. Is there a modifier to the row.Type = row.Dest statement that can select the entire last word from the original row? ... View more

Ok, I'm successfully updating the row - bigger achievement for me than you might think! 😉 But, I'm only getting the last character instead of the second word from the original row. Here's my script: # split table script #add field step (keep) import arcpy from arcpy import env inputTable = arcpy.GetParameterAsText(0) arcpy.AddMessage ("input " + inputTable) #list fields (stops duplicate add fields) theFieldList = arcpy.ListFields (inputTable, "Type") arcpy.AddMessage ("the count" + str(len(theFieldList))) #following exectues the add field (keep) if len(theFieldList) == 0:     arcpy.AddField_management(inputTable, "Type", "TEXT")     else:     arcpy.AddMessage ("Field Exists")     #split field loop rows = arcpy.UpdateCursor (inputTable)  #gets all vlaues for table for row in rows:  #loops through vlaues     row.Type = row.Dest[-1]     rows.updateRow(row) del row del rows I know I need to change the modifier on the row.Dest[-1] syntax but I thought the [-1] gave me the second word? ... View more