This tutorial shows the very basic steps to start building an Analytica model.

1. How to build a basic
model with Analytica

2. Creating a new model

3. When you start up
Analytica it shows
an Object window for
a new, untitled model.

4. Behind the Object
window you see an
empty Diagram window.

5. First you should
enter a Title for
your model...

6. Click in the Title field and give
your model a decent name.

7. When you hit Alt + Enter or the
Tab key or click somewhere outside...

8. ...the Identifier field automatically
changes to Car_cost_model based
on the Title you keyed in.

9. ...the Identifier field automatically
changes to Car_cost_model based
on the Title you keyed in.
The Identifier is automatically
created to match the first 20
characters of the Title.
You can change this
manually if you want.

10. If you like, type in a
description of your model...

11. ...or add your name as the author. (If your computer does not auto-matically register your name)

12. When you're done, close
the Object window...

13. ...and start building your
first model

14. Editing a diagram

15. But before we dive in let's
first explore the tools you
need in the tool bar.

16. When you create
a new model the
edit tool is selected
by default.

17. You use the edit tool to
create or change a model.
When you create
a new model the
edit tool is selected
by default.

18. When the edit tool
is selected, a menu
of icons is displayed
in the node palette.

19. When the edit tool
is selected, a menu
of icons is displayed
in the node palette.
These icons represent the different
node types and allow you to add
nodes to the diagram.

20. Creating variable nodes

21. Now you're going to
create variables in
the Car Cost model.

22. The first variable
you will create is
for the cost of fuel.

23. Drag the Variable Node
icon to a position in
the influence diagram.

24. Type Fuel cost for
the variable title.

25. Type Fuel cost for
the variable title. As you build a model, you should
choose descriptive titles for your
variables. Descriptive variable
titles remind you of the model’s
logic and help others to under-stand
how the model works.

26. Type Fuel cost for
the variable title. Since Fuel Cost doesn't yet
have a valid definition it's
filled with a diagonal line
pattern around its text.

27. Now you can repeat
this and create some
more variables that
affect fuel cost...

28. Price per gallon
of gasoline...

29. Number of miles
driven each year...

30. Miles per gallon
of gasoline...

31. And finally the
driver’s age.

32. Saving your model

33. After that it might
be a good idea to
save your model.

34. After that it might
be a good idea to
save your model.

35. After that it might
be a good idea to
save your model.
Analytica automatically saves each change you
make to a backup file. If your computer should
crash unexpectedly, you can recover your changes
the next time you start Analytica. Even so, it’s a
good idea to save your changes from time to time.

36. Deleting a variable

37. Sometimes you might want
to delete a variable that
you previously created.

38. In this example you realize
that the driver’s age is
not relevant to your
understanding of the Fuel
Cost variable.

39. When you hit Del or
Backspace ⌫ after selec-ting
the node, a confir-mation
dialog pops up...

40. Click OK to confirm
that you want to delete
the selected object.

41. Moving nodes

42. When you create a model you
should try to structure the
layout to make the influence
diagram easy to understand.

43. In this case you think that
Fuel Cost will be derived from
the other three variables.
Therefore you want to re-arrange
the diagram a little...

44. You move the
Fuel Cost node
to the right...

45. ...and place the
other variables
to the left.

46. Editing variable titles

47. Now you decide
that Mpg is still
a little cryptic...

48. So you rename the node
to Miles per gallon to
make things clearer.

49. When you change the title of
a node, Analytica asks you if
you want the Identifier to be
automatically changed as well.

50. When you change the title of
a node, Analytica asks you if
you want the Identifier to be
automatically changed as well.
You can change this behavior,
to either turn off automatic
updating of the identifier or to
make it fully automatic, so
that you are not asked.

51. Drawing arrows between nodes

52. One of Analytica’s most powerful
features is its ability to show
relationships between variables in
the influence diagram.

53. Influence arrows are used to specify
the dependencies between variables.

54. Because Miles per gallon
influences the Fuel Cost,
you want to draw an
arrow connecting the
two nodes.

55. Select the arrow tool
to begin drawing arrows.

56. Click on the node
where you want
the arrow to start...

57. ...and drag a line
to the other node.

58. When you release the
mouse button, the two
nodes are now connected
by an arrow, indicating
that Miles per gallon
affects Fuel Cost.

59. When you release the
mouse button, the two
nodes are now connected
by an arrow, indicating
that Miles per gallon
affects Fuel Cost.
When needed you can draw multiple
arrows at once. Just hold down
Control or Shift while selecting and
drag the lines to the desired node.

60. Entering attributes into
the Object window

61. Each variable (or other Object) has an
Object window that lets you see and
edit its Attributes, like its...

62. Each variable (or other Object) has an
Object window that lets you see and
edit its Attributes, like its...
Identifier

63. Each variable (or other Object) has an
Object window that lets you see and
edit its Attributes, like its...
Title

64. Each variable (or other Object) has an
Object window that lets you see and
edit its Attributes, like its...
Units

65. Each variable (or other Object) has an
Object window that lets you see and
edit its Attributes, like its...
Description

66. Each variable (or other Object) has an
Object window that lets you see and
edit its Attributes, like its...
Definition

67. Each variable (or other Object) has an
Object window that lets you see and
edit its Attributes, like its...
Inputs

68. Each variable (or other Object) has an
Object window that lets you see and
edit its Attributes, like its...
Outputs

69. If you want to
enter attributes for
Annual Miles, first
select the node...

70. ...then either click the
Object window button or just
double-click the selected
node on the diagram.

71. In the Object window you see that
Analytica has already assigned an
Identifier based on the Title.

72. In the Object window you see that
Analytica has already assigned an
Identifier based on the Title.
Analytica assigns the identifier when
the title is created. It uses the first
20 characters of the title except for
spaces or punctuation, which are
replaced by underscores (_).

73. You can directly edit both
the identifier and the title.

74. First, you change the
variable’s identifier to
a short abbreviation
so that it can easily
be used later in the
definitions of other
variables.

75. Then you type in
miles/year as the Unit
of measurement.

76. Then you type in
miles/year as the Unit
of measurement.
Analytica uses the information
from the Units field to label graphs
or tables that use this variable;
Analytica does not use it in any
mathematical computations.

77. When you change the
Title to Miles per year ...

78. ...Analytica asks you if you want
it to automatically change the
identifier to match the new title.

79. ...Analytica asks you if you want
it to automatically change the
identifier to match the new title.
In this case you click No to
keep the Identifier as Mpy.

80. Finally you enter
a description for
this variable.

81. Defining a variable as an explicit value

82. Analytica uses a wide range
of variable types. For now
we simply enter an explicit
value for the variable.

83. Analytica uses a wide range
of variable types. For now
we simply enter an explicit
value for the variable.
Functional expressions and lists,
for example, are described later
in this tutorial.

84. As a first guess you
put in a single number.

85. Click the Check button
to accept your input.

86. Miles per year is no longer
filled with a diagonal line
pattern around its title.
The clear node indicates
that this variable now
has a valid definition.

87. Defining a variable as a
function of other variables

88. When one variable
dependes on another
variable, you must
provide an expression
that describes the
relationship between
the variables.

89. Since you've drawn
arrows from other
variables to Fuel Cost,
their identifiers and
titles appear in the
variable's Inputs field.

90. Before you're going to define the functional
relationship you do a little housekeeping and
enter the Units and a Description.

91. Because fuel cost is equal to fuel price times
miles driven, divided by miles per gallon, you
will enter something equivalent to this into
the Definition field.

92. When you click into the Definition
field you can choose the Inputs
from a popup menu.

93. When you click into the Definition
field you can choose the Inputs
from a popup menu.
Variables that are not yet used in
the definition are display in italics.

94. Alternatively, when you start typing
a variable's name, Analytica's Expression
Assist provides a list of Identifiers and
Functions that start with the
letters you typed.

95. Based on the definition you just entered,
the value of Fuel Cost is calculated by
multiplying the values of Fuel Price and
Miles per year, and then dividing the result
by the value of Miles per gallon.

96. Entering attributes using
the Attribute panel

97. To calculate numerical
results for Fuel Cost we
still need to define the
other remaining inputs.

98. Otherwise, if you would
click the Result button, ...

99. ...you would get an error
message asking you if you
want to edit the variables
that are not yet defined.

100. When clicking YES the respective
variable node will be selected on
the diagram and you can edit
its definition right in the
Attribute panel below.

101. This is equivalent to opening the Object
window and editing the Definition there.

102. If you find it more convenient
to edit attributes using the
Attribute panel, you can
always click the Key icon to
open or close the panel.

103. Defining a variable as a list

104. In Analytica it's easy to
define an input not just as
a single number but, for
example, as a list of values.

105. This is especially useful
when you want to
perform WHAT-IF analyses.
Input Output

106. In order to see how
Fuel Cost is affected
by Miles per gallon, you
want to define this
variable as a list.

107. Because it's alway good practice, you
first enter a Description and the Units
before you're going to define the variable...

108. Now you want to define
it as a list of numbers
between 20 and 50, by
increments of 10.

109. From the Expression
popup menu you choose
List to enter a list of
numbers.

110. Then type 20 in
the first cell.

111. When you press Enter,
Analytica automatically
sets the next value
using the default
increment of 1.

112. Change the second cell
to 30 and press Enter.
Analytica automatically
sets the next value
using the increment
implied by the first
two values.

113. Now you have defined
Miles per gallon as a
range of values from
20 to 50.

114. Now you have defined
Miles per gallon as a
range of values from
20 to 50.
Although the auto-fill feature makes
it convenient to enter a simple linear
sequence, you are free to edit the
values as you please.

115. Viewing results in the Result window

116. Now that you have entered
attributes and definitions
for all variables it is time
to see the result.

117. To do so, select
the variable...

118. ...and click the
Result button.

119. The Result
window appears.

120. Icons in the upper left
corner of the Result
window control the
view mode.

121. Icons in the upper left
corner of the Result
window control the
view mode.
Graph view is the default.
But you can change this
in Preferences.