Generating histograms of multiple fields using ArcPy?

Question

I have a large shapefile and I'm trying to automate a process to generate histograms of several fields with the MakeGraph tool, but I'm receiving the following error.

class 'arcgisscripting.ExecuteError'>: Failed to execute. Parameters are not valid. ERROR 001020: Input series error. Incompatible parameter list. Click 'Always reset parameters...' check-box to reset parameters. Failed to execute (MakeGraph).

Any idea why this is happening? My inputs are as follows...

• input table = shapefile,
• fieldList is generated by input,
• workspace = output folder,
• input_template = a .grf or .tee (tried both),
• run is just a boolean true or false

Here's my code:

# Import arcpy module
import arcpy
# Check out any necessary licenses
arcpy.CheckOutExtension("spatial")
input_table = arcpy.GetParameterAsText(0)
fieldList = arcpy.GetParameterAsText(1)
workspace = arcpy.GetParameterAsText(2)
arcpy.env.workspace = workspace
input_template = arcpy.GetParameterAsText(3)
run = arcpy.GetParameterAsText(4)
countBin = 10
# Boolean selection
if run == 'true':
 # Iterate over selected field names
 for fieldName in fieldList.split(';'):
 out_graph_name = "histogram" 
 out_graph_jpg = fieldName + "_histogram.jpg" 
 # Create the graph 
 graph = arcpy.Graph() 
 # Add a histogram series to the graph 
 graph.addSeriesHistogram(input_table, fieldName, countBin) 
 # Specify the title of the left axis 
 graph.graphAxis[0].title = "Count" 
 # Specify the title of the bottom axis 
 graph.graphAxis[2].title = fieldName 
 # Specify the title of the Graph 
 graph.graphPropsGeneral.title = fieldName + " Histogram" 
 # Output a graph, which is created in-memory 
 arcpy.MakeGraph_management(input_template, graph, out_graph_name) 
 # Save the graph as an image 
 arcpy.SaveGraph_management(out_graph_name, out_graph_jpg, "MAINTAIN_ASPECT_RATIO", 600, 375)
else:
 print "done"

• fluidmotion: you mention the fieldlist is generated by input - can you verify that the fieldname is in the input table during the loop?
• cartoscience: fieldList is a field parameter with multivalues obtained from the shapefile and fieldName is each of the field names that are selected

Answer 1

Your issue is here I believe:

graph.addSeriesHistogram(input_table, fieldName, countBin)

Specifically, with the variable fieldName. For addSeriesHistogram, fieldNameneeds to be a layer object. Instead, it is a string in your code. To access the layer object, you'll need to use arcpy.ListLayers.

Try this code:

#Create map object
mxd = arcpy.mapping.MapDocument("CURRENT") 
#iterate through layer objects in map object
for lyr in arcpy.mapping.ListLayers(mxd):
 #Find layer with name 'fieldName'
 if lyr.name == fieldName: 
 graph.addSeriesHistogram(input_table, lyr, countBin)