[GIS] Getting maximum value from multiple values output (list of numbers) using Calculate Value in ModelBuilder

arcgis-desktoparcpymodelbuildermulti-values

I have an output from a sub model that iterates through feature classes, each with a row count. The row counts are passed to a collect values, which is a model parameter and is used outside the sub model.

How can i use simple code in a "calculate value" tool to get the maximum value from this list of numbers. I wish to then use this as a precondition to subsequent analysis so that if the sub model does not produce results then the subsequent analysis will not run.

This is similar to Exporting data from Collect Values output in ArcGIS ModelBuilder? that wished to use the actual list of numbers. The answer suggested an export to .csv file.

I only need to use a simple output so that I can use it as a pre condition on subsequent analysis. I have tried to calculate the Max(list), but it has not worked.

Best Answer

OK you have a model that is collecting values (of type long) and its a parameter. This is a sub model to the master model. In the master model connect your collection of values as a precondition to a Calculate Value tool. These collected values are called "Output Values".

In your Calculate Values tool:

Expression:

summe("%Output Values%")

Code Block:

import string
def summe(s):
  l = string.split(s,";")
  max = -1
  for i in l:
    if i > max:
      max = i
  return max

Data type:

Long

This approach is taking advantage of the fact that your collected values are "MultiValues" which are semicolon separated.

Example model finding the max value in a multivalue list

Related Solutions

[GIS] Exporting data from Collect Values output in ArcGIS ModelBuilder

You can do this using the Calculate Value (Data Management) tool and some Python magic. See also this related question: Add arbitrary code to Arcgis model builder?

A multivalue variable is just a semicolon-delimited string of values, so what the multivaluesToCsv function below does is split the multivalue variables into lists and transpose them into rows which are then written to a CSV (comma-separated value) text file.

Model iterators run ALL the processes in the model once per iteration -- this is undesirable for our Calculate Value tool, which we just want to run once at the end. The way you accomplish this is by creating another, outer model to wrap the original, inner model. This is discussed in the help topic Integrating a model within a model.

So here's what you need to do to get this working:

Inner Model - Iterates feature classes, processes them, collects values:

In your original model, which will be our "inner" model, add another Collect Values tool to collect the Name variable's values so that we can map the distance statistic values to their corresponding feature class names.
Expose the input and output variables as model parameters (right-click an oval and check Model Parameter). Do this for each of the outputs of the Collect Value tools as well as whatever input parameters you need such as the Input Workspace.
Save and close the inner model.

Outer Model - Runs inner model, runs Calculate Value tool just once when inner model completes:

Create a new model -- this will be our "outer" model.
Add a variable of type Folder to allow you to specify where to create the output CSV file.
Add a variable of type String to allow you to specify the name of the output CSV file.
Add the Inner Model to the new model (drag and drop from ArcToolbox or right-click and Add Data or Tool, browse to the inner model and click Add)
Create variables for any parameters of the inner model you want to be able to set from the outer model, such as the Input Workspace (right-click the inner model and and choose Make Variable-From Parameter).
Add the Calculate Value tool to the new model

Paste the following into the appropriate boxes of the Calculate Value tool:

Expression:

multivaluesToCsv(r"%Output CSV File Location%", "%Output CSV File Name%", "%Feature Class Names%", "%Minimum Distance Values%", "%Average Distance Values%", "%Maximum Distance Values%")

This uses in-line variable substitution to pass the model variables into the function. Adjust to match your model variable names.
The r before "%Output CSV File Location%" is significant: this indicates that this is a raw string; because Windows file system paths usually contain backslashes (an escape character in Python), we have to use this to prevent Python from misinterpreting the backslashes and subsequent characters as special character sequences.
Be sure to put quotes around the in-line variables because without them Python will think they are identifiers instead of strings.

Code Block:

import os, csv

def multivaluesToCsv(csvfilepath, csvfilename, fcnames, minvalues, avgvalues, maxvalues):
    ext = 'csv' # Define output file extension (e.g. csv or txt)
    header = ['FC', 'MIN', 'AVG', 'MAX'] # Define header row (column names)

    # Join CSV file path and name, adding extension if necessary
    csvfile = os.path.join(csvfilepath, os.extsep.join((csvfilename, ext)) if not os.path.splitext(csvfilename)[1].lower().endswith(ext) else csvfilename)

    # Open text file for writing
    with open(csvfile, 'wb') as f:
        w = csv.writer(f)
        w.writerow(header) # Write header row
        rows = zip(*map(lambda x: x.split(';'), [fcnames, minvalues, avgvalues, maxvalues])) # Transpose the semicolon-delimited values into rows
        w.writerows(rows)
    return csvfile

(Optional) Expose the input and output variables as model parameters if you want to be able to run them from the model's tool dialog or chain it together with other models/scripts. The sole output of the outer model is the CSV file.
(Optional) Connect the input variables and inner model outputs to the Calculate Value tool as preconditions. I do not think this actually has any effect, it just makes it more clear visually as to what's going on.

I have tested this with ModelBuilder and got it working (see screenshots).

Inner Model:

Outer Model:

The inner model runs all of its processes once per feature class, and then the Calculate Value tool runs once at the end to output the CSV file once and only once.

[GIS] Using field variable to calculate values in ModelBuilder

If you want a field picker you have to code it in python.

The code is as follows:

# Import system modules
import arcpy

# Set the parameters
InputFeatureClass = arcpy.GetParameterAsText(0)
InputField = arcpy.GetParameterAsText(1)

arcpy.SetParameter(2, InputField)

And the tool is set as follows:

Input Feature Layer

Data Type: Feature Layer (You might be using a Feature Set)
Direction: Input
Multivalue: No

Inputs Fields

Data Type: Fields
Direction: Input
Multivalue: No
Obtained from: Input Feature Layer

Output Field

Data Type: Field
Direction: Output
Multivalue: No

It looks like this

Toolbox Script dialog

You should then be able to use this to return a field as a FIELD object, suitable for a input parameter to the Calculate Field tool. A model looks like this: Example Model

I hope that helps.

Best Answer

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[GIS] Exporting data from Collect Values output in ArcGIS ModelBuilder

[GIS] Using field variable to calculate values in ModelBuilder

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