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Fundamentals of crime mapping basic arcview 9.2
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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