topic Re: How to transfer a query from R. Calculator to ArcPy in Python Questions

How to transfer a query from R. Calculator to ArcPy

KONPETROV — Mon, 16 Mar 2015 14:22:13 GMT

Hello,

I am using ArcGis 10.2. I have 3 classified rasters and i want to use the following query from r. calculator:

(rclslope>=45) & (rclmosaic>=2000) & (rclfocal>15) to arc.py

how can i write it?

Is it better to use local - combine tool with arc.py to do it?

Thank you very much.

Re: How to transfer a query from R. Calculator to ArcPy

DarrenWiens2 — Mon, 16 Mar 2015 15:47:25 GMT

You could use the Con tool (see this page for relevant examples):

Con(("rclslope">=45)&("rclmosaic">=2000)&("rclfocal">15),1)

This returns a raster with pixel value = 1 which meets the criteria. If you're looking for a way to spatially query pixel values in ArcGIS, that doesn't exist to my knowledge.

Re: How to transfer a query from R. Calculator to ArcPy

KONPETROV — Mon, 16 Mar 2015 18:05:15 GMT

thanks a lot Mr. Darren Wiens. But i need a little more help if you can. The entire code should seem like;

Re: How to transfer a query from R. Calculator to ArcPy

DarrenWiens2 — Mon, 16 Mar 2015 18:08:37 GMT

There are lots of arcpy examples using Con here - scroll to the bottom.

Re: How to transfer a query from R. Calculator to ArcPy

KONPETROV — Mon, 16 Mar 2015 18:11:27 GMT

So we mean something like that?

import arcpy

from arcpy import env

from arcpy.sa import *

env.workspace = "C:/sapyexamples/data"

outCon = Con(("rclslope">=45)&("rclmosaic">=2000)&("rclfocal">15),1)

outCon.save("C:/sapyexamples/output/outcon")

Re: How to transfer a query from R. Calculator to ArcPy

KONPETROV — Mon, 16 Mar 2015 18:16:47 GMT

Because with that i get an error

Re: How to transfer a query from R. Calculator to ArcPy

DanPatterson_Retired — Mon, 16 Mar 2015 18:27:41 GMT

well the error would help and you should have spaces between the grid names and the operands and perhaps it can't find the grids (assumed since there are no file extensions) And the big one is that you didn't make raster objects from you grid names. and please tell me that you have a path called c:/saexamples to test it in.

env.workspace = "C:/sapyexamples/data"

inRas1 = Raster("inRaster")

inRaster is inside the path

inRas1 is a Raster object which is needed by the Con statement

Re: How to transfer a query from R. Calculator to ArcPy

DarrenWiens2 — Mon, 16 Mar 2015 18:49:56 GMT

Agreed, mostly. What's this about spaces? AFAIK, they are irrelevant.

Re: How to transfer a query from R. Calculator to ArcPy

KONPETROV — Mon, 16 Mar 2015 20:26:44 GMT

Mr. Patterson i think i cannot understand you very well. I am still new in programming.

Re: How to transfer a query from R. Calculator to ArcPy

DarrenWiens2 — Mon, 16 Mar 2015 20:30:38 GMT

Please post the error.

Re: How to transfer a query from R. Calculator to ArcPy

KONPETROV — Mon, 16 Mar 2015 20:49:11 GMT

Runtime error

Traceback (most recent call last):

File "<string>", line 5, in <module>

File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\sa\Functions.py", line 244, in Con

where_clause)

File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\sa\Utils.py", line 47, in swapper

result = wrapper(*args, **kwargs)

File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\sa\Functions.py", line 228, in Wrapper

["IfThen", in_conditional_raster, in_true_raster_or_constant])

RuntimeError: ERROR 999998: Unexpected Error.

>>>

This keeps appearing with the following code:

import arcpy

from arcpy import env

from arcpy.sa import *

env.workspace = "C:/sapyexamples/data"

outCon = Con( ( "rclslope" >= 45 ) & ( "rclmosaic" >= 2000 ) & ( "rclfocal" > 15 ), 1 )

outCon.save("C:/sapyexamples/output/outCon")

Re: How to transfer a query from R. Calculator to ArcPy

DanPatterson_Retired — Mon, 16 Mar 2015 21:17:02 GMT

outCon = Con( ( Raster("rclslope") >= 45 ) & ( Raster("rclmosaic") >= 2000 ) & ( Raster("rclfocal") > 15 ), 1, 0 )

outCon.save("C:/sapyexamples/output/outCon")

Re: How to transfer a query from R. Calculator to ArcPy

KONPETROV — Mon, 16 Mar 2015 21:28:13 GMT

Mr. Wiens Unfortunately yes they exist!! Grid format also!! For God.

Mr. Patterson so finally we have that:

import arcpy

from arcpy import env

from arcpy.sa import *

env.workspace = "c:/sapyexamples/data"

outCon = Con( ( Raster("rclslope") >= 45 ) & ( Raster("rclmosaic") >= 2000 ) & ( Raster("rclfocal") > 15 ), 1, 0 )

outCon.save("c:/sapyexamples/output/outCon")

Right?

When i am loading it i am getting a raster with an attribute table with only one row and one colour all over the layer. No classes not anything. Why is that?

If i write the same proccedure in Raster Calculator (rclslope>=45) & (rclmosaic>=2000) & (rclfocal>15)

i ll get the result i want, here what am i doing wrong.

Re: How to transfer a query from R. Calculator to ArcPy

DanPatterson_Retired — Mon, 16 Mar 2015 21:45:38 GMT

the raster calculator is different that a script that uses rasters in a script. If the script gives you a result and you have a table, then you will have one of 2 values... 1 (where the condition is met) or 0 (where the condition is not met) A smart approach would be to use the Con tool in arctoolbox then if that works, go to the Results window and use that as the snippet for your code see my blog for examples related to Results and other programming tips

Re: How to transfer a query from R. Calculator to ArcPy

KONPETROV — Mon, 16 Mar 2015 21:50:57 GMT

Thank you very much sir, i ll try it

Re: How to transfer a query from R. Calculator to ArcPy

KONPETROV — Tue, 17 Mar 2015 01:01:47 GMT

Thank you both on of the problems was that : rclslope >= 45 !! e.g. rclslope it's already reclassified, so i just had to put slope. The other problem was something that had to do with my computer and Gis 10.2. so i put my computer on an earlier state to solve it. The code is working perfectly now with your corrections, that thing with spaces is very tricky.

Re: How to transfer a query from R. Calculator to ArcPy

DanPatterson_Retired — Tue, 17 Mar 2015 01:17:40 GMT

glad it is resolved ... tips for the future...never assume your inputs are correct, start from the beginning...always build incrementally, don't try to do a complex statement all at once, errors will be readily identified good luck