Fundamentals of Crime Mapping

Working with Tables in ArcMap

Attribute tables

The data behind the graphic

The ArcGIS ProjectRight click the theme to get

this dialog menu.

Click “Open Attribute Table” to see the data behind the

graphic

The Attribute Table

Field Names or Columns

“Options” button provides another

dialog menu that lets you

work with table data

A table can be added to a layout

or exported as DBF

Rows or Records

Add a new field, that can then be “calculated” or

manually entered

Add Field Types Name of New Field (10

Characters)

Field TypeOptions

Symbology Symbology properties

are different depending on if you are working with points, lines, or polygons.

The easiest is to work with is Single Symbol features where everything in the layer is displayed using the same symbol

Can use nominal, ordinal, ratio or interval data

Points Some symbol methods may not be useful (pie

charts for example) Markers

Lines

Some symbol methods may not be useful (pie charts for example)

Lines or Arcs

Polygons Nominal (categories), Ordinal, Interval and

Ratio (Quantities) can be used with different methods

Fills and outlinesNominal data

example

Ratio Data Example

Symbology

Category data symbology comes next

It displays data by unique values of a field, or multiple fields

Nominal, ordinal, ratio or interval data

Symbology

Next, comes the quantities

symbology method

It uses a number field in the table

to display data by classified values

Ratio and interval data

Quantities Classifications

Six different ways to classify data, with an added manual method for infinite freedom

Classification Methods

Equal Interval Defined Interval Quantile Natural Breaks Geometrical Interval Standard Deviation

Types of Data Categorical (Qualitative)

◦ Grouping based on some quality◦ Labels or categories◦ E.g.; Sex = Male or Female◦ Nominal or Ordinal

Nominal the order is not important E.g.: Sex = male or female

Ordinal the order is important E.g.; Rank = Officer, Sergeant, Lieutenant, etc

◦ Can be binary or non-binary Binary = only two values (male or female) Non-Binary = More than two (red, blonde, brunette,

etc)

Types of Data Measurement (Quantitative)

◦ Grouping based on some quantity or value◦ Always numbers◦ Discrete or continuous

Discrete = only certain values are possible and data could have gaps (1, 2, 3, or 4)

Continuous = Any value along some interval (any value between 1 and 4 (ie: 3.24211)

◦ Interval or ratio In interval data the interval between values is

important (ie; temperature of 30 compared to 110 means something)

Ratio data is the best, and the “0” value can be informative (ie; a grid can have 0 crimes, or any value up to infinity)

Great Website to Explain Research and Data Types

http://www.socialresearchmethods.net/kb/index.php

Classification Methods

Equal Interval (ratio, Interval)◦ The range between the classifications is

the same

Take thehigh value-low value and for each of the 5 classes, the

value is 199.61

Number of classes desired

determines interval

Classification Methods Defined Interval (ratio, interval)

◦ Similar to the equal interval, but here, we define what the interval will be and thus establish the classes

In this case the interval was set to 150, and so the number of

classes is determined by

the interval

Classification Methods Quantile (ratio, interval)

◦ A percentage of the values in the class falling with the range. Each class contains an equal number of features.

Each of the 10 classes has the same number of features within each class, or makes up 10%

of the total records

Classification Methods Natural Breaks (ratio, interval)

◦ Breaks the data where there are natural holes between values

Use test exam score example

Classification Methods Geometrical Interval (ratio, interval)

◦ This is a classification scheme where the class breaks are based on class intervals that have a geometrical series. This ensures that each class range has approximately the same number of values with each class and that the change between intervals is fairly consistent.

The interval is determined by a

geometric equation (large

and small changes

depending on breaks in data)

Classification Methods Standard Deviation (ratio, interval)

◦ Classes are determined by mean and standard deviation of values. Can display by 1, ½, ¼ standard deviations as needed

Automatic Labels Right click the theme and choose properties,

then choose the Labels tab

Can label all features the

same, or use a query to label

features differently

Use a field in the data for the

labels that is good

Infinite text choices

You can combine fields

for labeling

Control over placement options, scale at which labels draw and styles are

available

Select by Attributes Use to select data by a SQL query

Click this