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Amos 4.0 User’s Guide Tutorial: Learning to Program Amos with Visual Basic · 45
Tutorial: Learning to
Program Amos with Visual
Basic
Purpose
You can use Amos 4.0 as a component in the
computer programs you write. It is a relatively
easy process because Amos lets you work in a
general-purpose programming language instead
of having to learn some special language. To use
Amos 4.0 with your program, you need to
program in a language or environment that can control automation servers, e.g.,
Microsoft Visual Basic, Microsoft C++, the SPSS scripting facility, SAS, DEC
Visual FORTRAN or Borland Delphi1.
The program that you write can carry out a single Amos analysis, or multiple
Amos analyses. It can also include statements that:
· specify a model
· give the location of data files
· select options, such as: which discrepancy function to use, whether to obtain
bootstrap confidence intervals, and so on.
This section demonstrates in detail how you can call Amos 4.0 from the Microsoft
Visual Basic Professional Edition2, Version 5.0. It assumes that Microsoft Visual
1 At the time of this writing, there have not been any attempts to use Amos 4.0 with SAS, Visual
Fortran, or Borland Delphi.
46 · Tutorial: Learning to Program Amos with Visual Basic Amos 4.0 User’s Guide
Basic Professional Edition is installed on your system. The Visual Basic files for
this tutorial are StartVB.vbp (VB project) and StartVB.bas (VB code). You
will find both located in the Tutorial subdirectory underneath the Amos 4.0
program directory.
1. Create a new Visual Basic project
First, launch Visual Basic. In the New Project window, click on the New tab and
double-click on Standard EXE.
2 Microsoft offers several other Visual Basic packages with varying capabilities. Most of these
can be used with Amos 4.0, but different steps may be required to reference the Amos Engine.
Amos 4.0 User’s Guide Tutorial: Learning to Program Amos with Visual Basic · 47
2. Remove Form1
If this is the first time you have used Visual Basic since its installation, the Visual
Basic window will probably look something like this:
Many of the elements in the Visual Basic window are useful only when you are
writing a program that has a graphical interface. These elements are not needed for
this tutorial, so we will get rid of them.
48 · Tutorial: Learning to Program Amos with Visual Basic Amos 4.0 User’s Guide
In the Project1 window, use the right mouse button to click on Form1 (Form1) as
indicated by the mouse pointer in the preceding figure. When the following pop-up
menu appears, select Remove Form1:
Amos 4.0 User’s Guide Tutorial: Learning to Program Amos with Visual Basic · 49
3. Hide unnecessary windows
Hide the VB toolbar by clicking the X button indicated by the mouse pointer in the
following figure:
Also, hide the three sub-windows titled Project - Project1, Properties - Project1,
and Form Layout - Project1. (Do not hide the sub-window titled Immediate.)
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The resulting Visual Basic window should look like this:
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4. Create a code window for your program
On the menu, select Project and then Add Module:
52 · Tutorial: Learning to Program Amos with Visual Basic Amos 4.0 User’s Guide
In the Add Module window, select the New tab and double-click on Module:
Amos 4.0 User’s Guide Tutorial: Learning to Program Amos with Visual Basic · 53
The Visual Basic window will then look something like this:
54 · Tutorial: Learning to Program Amos with Visual Basic Amos 4.0 User’s Guide
5. Tell Visual Basic how to find the Amos Engine
In order to let Visual Basic know that you want to use the Amos Engine, select
Project from the main menu, and then References:
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When the References - Project1 dialog appears, make sure that the Amos Engine
box is has a check mark in it. If necessary, click on the Amos Engine box to add a
check mark. Then press the OK button to close the dialog:
6. Enter your program
Type the following program in the large panel in the Visual Basic window.
Option Explicit
Sub main()
Dim Sem As New AmosEngine
Sem.TextOutput
Sem.BeginGroup Sem.Dir & "Tutorial\Hamilton.dbf"
Sem.Structure "SAT = (w1) Education + (w2) Income + (1) Other"
Sem.FitModel
Debug.Print "Regression weight 1 is "; Sem.ParameterValue
("w1")
Debug.Print "Regression weight 2 is "; Sem.ParameterValue ("w2")
Debug.Print "Chi square = "; Sem.Cmin
Debug.Print "Degrees of freedom = "; Sem.df
End Sub
56 · Tutorial: Learning to Program Amos with Visual Basic Amos 4.0 User’s Guide
Instead of typing these commands, you can also insert the StartVB.bas file from
Amos 4.0’s Tutorial subdirectory. With the code window active, run Edit ®
Insert File... and select StartVB.bas located by default in the C:\Program
Files\Amos 4\Tutorial directory. Sem.Dir is an Amos Engine property
that returns the path to where the Amos program is found. The VB string
expression:
pinpoints exactly where the data file resides.
The Visual Basic window should look like this:
Sem.Dir & "Tutorial\Hamilton.dbf"
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7. Run the program
To run the program, select Run from the main menu, and then Start with Full
Compile:
When the program has finished running, the output from the Debug.Print
statements appears in the Immediate panel:
8. Try out the help system
Before closing the Visual Basic window, try the help system. Click somewhere
within one of the words that describes an Amos method in your program:
TextOutput
BeginGroup
Structure
FitModel
ParameterValue
Cmin
Df
Then press the F1 key. A dialog box will appear giving documentation for that
method. To get a list of all available methods, press the F2 key to display Visual
Basic’s Object Browser. In the Classes listbox, click on AmosEngine.
58 · Tutorial: Learning to Program Amos with Visual Basic Amos 4.0 User’s Guide
All the available methods will appear in the listbox labeled Members of
‘AmosEngine’:
Click once on a method to see a short summary of its function in the bottom panel.
Press F1 to see the full documentation of the method.
Beyond the basics
Still seeking more information about how to use Amos 4.0 as a component in the
computer programs you write? Extensive, advanced reference material for the
Amos API is also included in the Amos 4.0 Programming Reference Guide. This
guide is available as a downloadable Portable Document Format (PDF) file from
the Amos 4.0 CD-ROM or as a Help file from either the Amos Graphics or Amos
Basic Help menu.