Key Ideas in Lab #4:

1. Handling one-to-many relationships in ArcMap
   • Tricky to map population density when towns may have more than one part (polygon).
   • Common complication since geometry and data tables come from different sources
   • More common with detailed (large scale & small area) maps - Boston has more than one 'part'
2. Constructing meaningful indices:
   • Requires excluding cases and normalizing data
   • Mmay require creation of new features and attributes in writeable directories.
3. Charts and business graphics in ArcMap
   • Another dimension added: linking map/table/chart

Key Techniques in Lab #4:

1. Joining attribute tables in ArcMap
• Identify matching columns for each table
• Direction matters! start with geographic table
• Join handles only one match per row!
2. Summarizing ArcMap attribute tables: Aggregating across rows
• Highlight the 'group by' column (where each unique value results in one output row)
• Select other columns that you wish to aggregate (via 'count,' 'sum,' 'max,' etc.)
3. Charting the correct table
   • May need to 'summarize' a table before charting
   • Be careful about which table to join to maps (i.e., the one-to-one table after summarization)
   • Selecting on map can impact chart as well as highlighting attribute table rows (if correct tab is checked)

Debriefing (about prior labs and homework):

1. Resetting ArcGIS configuration files:
   • user customizations are saved in H:\WinData\Application Data\ESRI
   • The ArcMap template file is: H:\WinData\Application Data\ESRI\ArcMap\Templates\normal.mxt
     
   • Phil Thompson's commands erase the ESRI subdirectory (and related registry setting) requiring a clean copy when restarting ArcGIS
     • Exit from ArcGIS apps and run these two commands in a ' command prompt' window:
     • reg delete hkcu\software\esri
     • rmdir /s /q "%APPDATA%\esri"
       
2. Debugging skills: Verify success of each step of many-step procedure:
   • If buffering: are there rows in the attribute table of the features to-be-buffered?
   • If adding columns, summarizing, calculating: do you have write-access to the feature shapefile?
3. Customizing layers:
   • Shapefiles (and coverages) on disk (or in SDE):
     • Stores all retained information (including projections, indices)
     • Need write access to change
   • Layers in ArcMap
     • Can view in different projection by setting active 'data frame' projection
     • Can exclude features (rows) via command in layer properties
     • Can manipulate only 'selected features' or 'all features' with most operations
     • Can 'export' shapefile and/or table of selected features to writeable space
     • Can retain symbology and other settings by saving as 'layer' in personal geodatabase
     • Can have more than one 'copy' of the same shapefile (or coverage) in a data frame
       

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