How to perform Intersection using ModelBuilder iteration?

Question

I would like to take the intersection of two areas (one randomly generated), and do this n times. I can do it and get one result, but I can't save all the intersection areas to a file at the end.

The problem is that when I run my model more than once it says that my buffer output file already exists, which I can imagine would happen again for the intersection. What I'd like to happen is to run my model where I produce new random points everytime, then buffer them and intersect the dissolved buffer with another area and then get out the area. Then I want to do this several times.

If this isn't worded very well then just let me know and I can explain what I mean in another way. Thanks a lot

Answer 1

In model builder, to avoid overwrites in iterators, you have to use inline variables. See ESRI help:

http://resources.arcgis.com/en/help/main/10.1/index.html#//002w0000005w000000

For your particular use case, example 2 explain what you have to do:

When the iterator Iterate Feature Classes runs, it creates an output variable for both the path and name of the feature class. The value in the Name variable can be used to construct the path to the projected feature class. When the tool executes, %Name% is replaced with the name of the feature class.

Answer 2

Two additions should make this work assuming I understand what you're looking to do here.

Setting the overwrite environment variable to true will skip errors where the dataset already exists. Since you only need random points within the loop we can get rid of them after each iteration.

Second, if you set up a loop, you can append your counter to the filename when you run your intersect. This will save all of your files rather than overwriting them. If you'd rather have more descriptive names you could create a python list (example below), and append an item from that list to the filename on each iteration.

# example of a python list
list = ["filename1", "filename2", "filename3"]

To access the item in a list, use the counter in the loop.

# While the counter is less than the length of the list (we start counting from 0 instead of 1) print the list item
i = 0
while i < len(list):
    print list[i]
    i += 1

Example code:

# Import arcpy module
import arcpy
arcpy.env.overwriteOutput = True

# Local variables:
Python_Intersect_prac = "D:\\Python_Intersect_prac"
Plume_dissolve1 = "Plume_dissolve1"
Random_Hs_shp = "D:\\Python_Intersect_prac\\Random_Hs.shp"
Random_Hs_b_shp = "C:\\Users\\c1022376\\My Documents\\Random_Hs_b.shp"
Random_Hs_b_Intersect = "C:\\Users\\c1022376\\My Documents\\ArcGIS\\Default1.gdb\\Random_Hs_b_Intersect"

# Initialize counter
i = 0

# How many times would you like to loop? (integer)
j = 5 # this will run 5 times

# the following code will iterate j times
while i < j:
    # Process: Create Random Points
    arcpy.CreateRandomPoints_management(Python_Intersect_prac, "Random_Hs", "", "-180 -90 180 90", "35", "0 Unknown", "POINT", "0")

    # Process: Buffer
    arcpy.Buffer_analysis(Random_Hs_shp, Random_Hs_b_shp, "4 DecimalDegrees", "FULL", "ROUND", "ALL", "")

    # Process: Intersect
    arcpy.Intersect_analysis("'C:\\Users\\c1022376\\My Documents\\Random_Hs_b" + i + ".shp' #;Plume_dissolve1 #", Random_Hs_b_Intersect, "ALL", "", "INPUT")

    # Iterate the counter
    i += 1