ESRM 250/CFR 520 Autumn 2009 Phil Hurvitz

ESRM 250 & CFR 520: Introduction to GIS

© Phil Hurvitz, 1999-2009

ESRM 250/CFR 520Autumn 2009Phil Hurvitz

Tables

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Using ArcMap tablesQuerying tablesTable relationshipsGraphs from tables

Overview

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Tables are just as important as coordinate (map) data

Tables are used to hold attribute data Tables can be used to hold data that are

not explicitly spatial in nature Tables are the source of all basic statistics

Using ArcMap tables: Introduction

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Creating tables from existing sources Creating a new tableAdding fields (columns) to tablesAdding records (rows) to tables Editing values in table recordsCalculating fields

Using ArcMap tables: Overview

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Tables can be created from existing sources:

dBase files ASCII files

(tab or comma delimited) INFO files ODBC

connections

Creating tables from existing sources

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Tabular data can be obtained from ODBCdatabases (e.g., Oracle, Access)

Creating tables from ODBC connections

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New (dBase, GDB) tables can be created from scratch

Creates a new file on disk New table is empty

Creating a new table

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Each field must be defined at add timeData type and storage parameters

need to be defined

Adding fields to tables

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Field data types should match the data they will store

Short Integer: Whole numbers from -32,768 to 32,768

Long Integer: Whole numbers from -2,140,000,000 2,140,000,000

Float: single-precision floating-point numbers with an accuracy to 6 places past the decimal

Double: double-precision floating-point numbers with an accuracy to 15 places past the decimal

Date: January 1, 0100 to December 31, 9999 Text: 1 - 255 characters

Tips for defining fields

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Precision = number of digitsScale = digits to the right of the

decimal point

e.g., 100.27

precision = 5scale = 2

Tips for defining fields

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Records can be added ad hoc to stand-alone tables

Do not add records to feature data (point, line, polygon) tables

Adding features (feature editing) will automatically add a record to the feature attribute table

Adding records to feature attribute tables will result in “phantom” records that are not associated with shape features

Adding records to tables

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Records can be added ad hoc to stand-alone tables

New records will have null values for all fields until updates are made

Adding records to tables

new record

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Values in a new field can be generated based on calculated expressions

Expressions can use other fields

Acts on selected set of records

Calculating fields

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Overview

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Making queriesSorting recordsDisplaying selected setsModifying selected setsBasic descriptive statisticsTable summaries

Querying tables

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Select records from tables “Select by attributes” Graphical interface to

table data Selected records in cyan

Making queries

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Displaying selected records will show only those records that are in the selected set

Displaying selections

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Record can be sorted ascending or descending by field

Sorting records

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Selecting records from feature tables also selects features from layers (and vice versa)

Displaying selected sets

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Existing selections can be broadened or narrowed

Additional query criteria Add to selection Remove from selection Further narrow down

current selection

Modifying selected sets

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Basic descriptive statistics can be generated for a field

will describe selected set (or all records if there is no active selection)

Basic descriptive statistics

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Summarizing tables Creates a new table Summarizes values in numeric fields by

values in a categorical field One output record per unique value in the

(categorical) field of interest Different summary statistics available

Table summaries

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Table summaries

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Overview

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One-to-one relationship every record in Table A has a matching

value in Table B

Record relationships among tables

Table B

Table A

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Many-to-one relationship Many records in Table A have a match with

only 1 record in Table B


Table B

Table A

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One-to-many relationship Only 1 record in Table B has a match with

many records in Table B


Table B

Table A

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Creates a virtual join (does not alter data sources)

Used for: one-to-one many-to-one

Joining tables

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Does not join, but allows simultaneous selections

Used for: one-to-one many-to-one one-to-many

Relating tables

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“Relate” updates the selection on the related table based on field relationships

Relating tables

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Overview

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What are graphs?Creating graphs from tablesGraph elementsGraph typesGraph legendsAxis propertiesAxis increments and grid linesDisplaying multiple fields

Making graphs from tables

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Graphical representation of tabular data

What are graphs?

numbers can bedifficult to interpret

graphs are easier to interpret

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Graphs are dynamically linked to tables

A selection on the table will be reflected in the graph

What are graphs?

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Creating graphs from tables

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Creating graphs from tables

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Graph elements

Graphs havemanyelementsto format

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A number of different types and subtypes of graphs exist

Graph types

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X and Y axes have various properties

Axis properties

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Increments and grid lines can be formatted in different ways

Axis increments and grid lines

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A maximum value can be specified Be careful, the graph no longer shows the

data range

Axis increments and grid lines

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Multiple fields can be displayed in the graph

Comparison of variables

Displaying multiple fields

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Documents

ESRM 250/CFR 520 Autumn 2009 Phil Hurvitz