topic Re: deflection angle script in Python Questions

deflection angle script

JimFritz — Sat, 11 Dec 2021 21:08:09 GMT

After running the script below the "point" layer that is created does not have any features and of course no angles calculated. Any ideas on why this might be would be appreciated.

Thanks,

Jim

import math  
02.... sr = arcpy.Describe("Z77").spatialReference    
03.... arcpy.CreateFeatureclass_management('in_memory','points',"POINT",spatial_reference=sr)  
04.... arcpy.AddField_management('points','Angle',"DOUBLE")  
05.... insCur = arcpy.da.InsertCursor("points",('SHAPE@','Angle'))  
06.... with arcpy.da.SearchCursor("Z77",["SHAPE@"]) as cursor:    
07....    for row in cursor:    
08....        for part in row[0]:      
09....            pt_count = 1    
10....            for pnt in part:    
11....                pnt = arcpy.PointGeometry(pnt,sr)    
12....                if pt_count > 1:    
13....                    if pt_count >2:    
14....                        distAB = oneBack.distanceTo(twoBack)    
15....                        distBC = pnt.distanceTo(oneBack)    
16....                        distAC = pnt.distanceTo(twoBack)    
17....                        angB = math.degrees(math.acos((((distAB*distAB)+(distBC*distBC))-(distAC*distAC))/(2*distAB*distBC)))  
18....                        insCur.insertRow((oneBack,angB))   
19....                    twoBack = oneBack    
20....                oneBack = pnt    
21....                pt_count += 1  
22.... del insCur  
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Re: deflection angle script

DarrenWiens2 — Thu, 29 Nov 2018 18:09:09 GMT

Add some print statements, particularly before you try to insert, to ensure the values are what you expect. If not, or if the print never executes, back up and figure out where it's failing.

Re: deflection angle script

JimFritz — Thu, 29 Nov 2018 18:25:44 GMT

Darrin,

Thanks, I will try the print statement remedy. Also, can the input "lines" layer be either a dissolved polyline feature or a multi-part polyline feature?

Jim

Re: deflection angle script

DarrenWiens2 — Thu, 29 Nov 2018 19:02:06 GMT

The line(s) must be multi-part (i.e. many line segments joined into one feature).

Re: deflection angle script

JimFritz — Thu, 29 Nov 2018 20:00:52 GMT

Darren,

Note nothing returned.

Thanks for the help!!

Jim

Re: deflection angle script

DarrenWiens2 — Thu, 29 Nov 2018 20:17:35 GMT

That means there's either no pnts in part, or no parts in row[0], or no rows in cursor.

Re: deflection angle script

JimFritz — Thu, 29 Nov 2018 20:26:04 GMT

Hmm, just noticed that prior to running script there was attribute field called "angle" and populated from some earlier tinkering. I just deleted it so I will re-run the script.

I really appreciate the help! I see that the script does work so just have to keep plugging away at it. I don't have much more time today but will pick up again tomorrow.

Regards,

Jim

Re: deflection angle script

JimFritz — Thu, 29 Nov 2018 20:35:43 GMT

Darrin,

Just to make sure I understand the "no pnts in part, or no parts in row[0] " is in reference to the multi-part polyline layer (Z77_UTM13splitatpoint)??

Thanks,

Jim

Re: deflection angle script

DarrenWiens2 — Sat, 11 Dec 2021 21:08:12 GMT

For some reason, your print statements aren't printing because the code never gets to them, so you need to back-track to figure out where the problem is. See which prints get executed. If nothing, there would seem to be a problem in the feature class itself.

with arcpy.da.SearchCursor("Z77",["SHAPE@"]) as cursor:    
    for row in cursor:    
        print('this is a feature')        
        for part in row[0]:
            print('this is a part in the feature')      
            pt_count = 1    
            for pnt in part:
                print('this is a point in the part in the feature')
                ...‍‍‍‍‍‍‍‍‍

Re: deflection angle script

JimFritz — Fri, 30 Nov 2018 15:28:07 GMT

Darren,

I used the code above and as you can see above nothing is printed. The feature class appears normal (a polyline) with 111 segments. Not sure what is going on here.

Thanks,

Jim

Re: deflection angle script

JimFritz — Fri, 30 Nov 2018 15:32:23 GMT

Darren,

Disregard the last response. Print statements seem correct. Going back to original script now.

Thanks,

Jim

Re: deflection angle script

JimFritz — Fri, 30 Nov 2018 16:02:33 GMT

Darren,

Here's the latest results using the original script. Seems the print functions are working up to "print (angB)" and then nothing is returned. Any ideas?

Re: deflection angle script

DarrenWiens2 — Fri, 30 Nov 2018 18:43:55 GMT

Check your indentation and notice that pt_count never gets incremented, so it's never > 1.

The idea to debug this is to try to figure why the print statement never gets executed, which is because it never gets into the loop. Why not?

Re: deflection angle script

JimFritz — Fri, 30 Nov 2018 19:13:51 GMT

Thanks, I'll double-check the indentation issues when pasting in the code to the python window.

Re: deflection angle script

DanPatterson_Retired — Fri, 30 Nov 2018 19:16:45 GMT

print pnt_count rather than the point object

Re: deflection angle script

JimFritz — Fri, 30 Nov 2018 19:28:55 GMT

Would that be coded like this?

.....

......

pt_count = 1

print (pt_count) or print("pt_count")

thanks,

Jim

Re: deflection angle script

JimFritz — Fri, 30 Nov 2018 21:55:45 GMT

Thanks Darren and Dan. It came down to incorrect indentation.

Problem solved!