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Overview and Notes
Vensim Help
Legal Notices
License Agreement
Technical Support
ReleaseNotes
Current Changes
SyntheSim
Behavior Changes
Function and Language Changes
DLL Venapp and Command Changes
Changes from Vensim 4
Changes from Vensim 3
Model Reader Notes
Overview
Main Menu
Toolbar
Control Panel
Subscript Control
Simulation
Graphs, Tables and more
Vensim Information
Vensim Demo Notes
Vensim Demonstration Help
Vensim Demo
General Instructions
Sample Models
Development Environment
Using Existing Models
Building Dynamic Models
Venapp Help
Main Menu
Review Structure
Scenario Setup
Simulation Setup
Analysis Control
Predefined Graphs
Trace Causes with Tree
Trace Causes with Graphs
Trace the Uses of a Variable
Contact Information
User's Guide
1 Introduction
About Vensim
About this User's Guide
How this Guide is Organized
Style Conventions
About Directories
About Screen Shots
About the Mouse
About Tab Dialog Boxes
Installing Vensim
Start the Installation Program
License Agreement
Registration Code
Installation Directory
Other Vensim Configurations
Other Resources
2 The Vensim User Interface
Main Features
Title Bar
Menu
Toolbar
The Window Classes
Moving Among Window Classes
Moving Among Windows within a Class
The Build Window
Sketch Tools
Status Bar
Simulating
Output Windows
Analysis Tools
Analysis Tool Output
The Control Panel
Subscript Control
3 A Hands-On Example
Modeling with Vensim
The Workforce Inventory Example
Starting Vensim
Opening the Model
Examining Structure
Simulating the Model
Examining Behavior
Causal Tracing
Individual Simulation Experiments
Making a Custom Graph
Making a Custom Table
Summary
4 Causal Loop Diagramming
Vensim Models
Drawing Sketches
Mouse Tips
Constructing a Causal Loop Diagram
Project Model
Modifying diagrams
Sketch Layout
Sketch Options
Adding Comments and Graphics
Refining the Model
Printing and Exporting the Sketch
Structural Analysis of Diagrams
Causal Tracing with Trees
5 Stock and Flow Diagrams
Overview
Building a diagram
Entering Levels
Creating Rates
Bending Rate Pipes
Adding Auxiliaries and Arrows
More Structure
Customizing Diagrams
Sketch Options
Variable Shapes
Default Sketch Options
Hiding Sketch Elements
Resizing the View
Modifying the Sketch Tools
6 Building a Simulation Model
A Population Model
Vensim Conventions
Sketching the Rabbit Model
Writing Equations
Checking for Model Syntax and Units Errors
Units Equivalents
Simulating the Model
Model Analysis
Comparing Simulations
Exponential Growth
Simulation Experiments
Causes Strip Graph
Runs Compare
Exponential Decay
Input and Output Objects
7 Functions and Simulation Errors
Overview
Price and Demand
Entering a Function
IF THEN ELSE
SMOOTH
STEP
Initial Conditions
Model Equations
Simulation Errors
Errors at Time Zero
Errors During the Simulation
Mysterious Oscillations
Errors Integrating
Model Corrections
XIDZ
8 Building a Function with Lookups
Overview
Limits to Rabbit Growth
Normalized Lookups
Sketching the Model
Entering Equations
Creating and Normalizing Lookups
Editing Values
Checking for Model Syntax and Units Errors
Simulating the Model
Model Analysis
Separate Normalized Variables
Simulation
Changing Model Lookups
Named Lookups
9 Multiple Views
Overview
How Views Work
Customer Diffusion Model
Building the Diffusion Model
Simulating the Model
Model Analysis
Naming and Saving Your Model
Adding the Capacity View
Shadow Variable Tool
Adding Equations
Altering An Equation
Adding a Sales Revenue View
Model Variable Tool
More Equations
Simulating the Model
Analyzing the Model
Saving Your Model
Detailed Capacity Model
Copying and Pasting
Capacity View Equations
Units Synonyms
Simulating and Analyzing the Model
Capacity Investment Policy
10 Customizing Output
Overview
Output from Analysis Tools
Graphs and Strip Graphs
Graphs Lines with Markers
Tree Diagrams
Custom Graphs
Custom Tables
11 Games in Vensim
Overview
What Are Games?
The Real Estate Game
Model Structure
Built-in Functions
WIP Graph
Adding Game Variables
Simulating the Model
Playing the Game
Moving Forward in a Game
Backing Up in a Game
12 Input Output Controls
Overview
Word of Mouth Sales
wom1.mdl Equations
Output Controls
Input Controls
Gaming Control
Publishing the Model
Game Interval
Commentary and Navigation Links
Test It Out
Publish a Package
13 SyntheSim
Overview
Simple Arms Race Model
New Diagramming Flourishes
Min, Max and Increment
Model Equations
Structure, Behavior and Speed
Showing Behavior
Making Simulations
Changing Lookups
Changing from the Toolbar
Doing Simulation Experiments
Loading and Unloading Runs
Breaking Feedback Loops
Stopping the Race
Overriding Behavior
Building a Control Panel
Subscripts and SyntheSim
14 Reality Check
Overview
Models and Reality
Domains of Expertise
Defining Reality Check Equations
Test Inputs
Constraints
Simulation and Reality Check
Active Constraint Checking
Passive Constraint Checking
Error Reporting
Entering Reality Check Equations
Equation Editor
Running Reality Check
The Reality Check Tool
Reality Check Results
Reviewing Simulation Results
Reality Check and Yeast Growth
Test Input and Constraint Equations
An Initial Model
Temperature, Divisions and Terminations
Divisions as influenced by Water and Sugar
Water and Sugar as Influenced by Divisions
Conclusion
15 Sensitivity Testing
Overview
Monte Carlo Simulations
Market Growth Model
Sales.mdl Equations
Base Simulation
Uncertainty in Multiple Parameters
Sensitivity Control Parameters
Random Uniform Distribution
Random Normal Distribution
Save Lists
Sensitivity Simulations
Time Graph Sensitivity Output
Confidence Bounds
Focusing Graph Scales
Individual Traces
Histogram Sensitivity Output
Changing the Default Analysis Toolset
Stats Tool
16 Using Data in Models
Introduction
Types of Data Use
Using Data to Drive a Model
Getting Data from a Spreadsheet
Simulating
Data Variable with Imported Data
Importing Text-Formatted Data
Simulation
Importing Spreadsheet Data
Simulation
17 Subscripts
Overview
Introducing Subscripts
A Simple Project Model
proj1.mdl Equations
The Subscript Range
The Subscript Control
Adding Subscripts to Variables
Constant Equations
Vector Functions
Subscripts in the Equation Editor
Subscript Summary
Simulation and Analysis
Advanced Subscript Model
Subscript Range
Mapping Subscripts
Multiple Equations for a Subscripted Variable
Logical Functions and Operators
VMIN Function
Simulation and Analysis
18 Optimization
Overview
Model Calibration
Electric.mdl Equations
Comparing to Data
Setting the Payoff
Setting Optimization Parameters
Computing Confidence Bounds
Optional Modifying the Model
Policy Optimization
Inventory Stock Model
Setting the Payoff
Setting Optimization Parameters
19 Sending Models to Others
Overview
Vensim Model Reader
Preparing the Model
Publishing a Pakaged Model
Opening a Packaged Model
Using models with Vensim PLE
Email and Web Notes
20 Reference Modes
Overview
Conceptualization with Reference Models
Closing the Loop
Simulating
Mental Integration
Managing Reference Modes
Appendix Information Resources
Overview
System Dynamics Books
Roadmaps
Publishers
System Dynamics Society
Internet Resources
Support and Licenses
Support and Services
Standard Professional and DSS Support
PLE and PLE Plus Support
Software License
Modeling Guide
1 System Dynamics Overview
Overview
Events, Behavior and Structure
The System Dynamics Process
Fundamental Structures and Behaviors
Exponential Growth
Exponential Decay
S Shaped Growth
Oscillation
2 Workforce, Inventory and Oscillation
Overview
Background
Reference Modes
Reality Check
Dynamic Hypothesis
Workforce / Inventory Model
Workforce
Behavioral Relationships
Equation Set wfinv1.vmf
Analysis
Model Refinement
Additional Equations
Refined Model Behavior
Phasing and Oscillation
Sensitivity
Extensions and Exercises
3 Project Dynamics
Overview
Task Accomplishment
Stopping Work
Integration Techniques
Errors and Rework
Rework Discovery
Schedule
Workforce and Hiring
Willingness to change workforce
Project Restarts
Resulting Behavior
Schedule Pressure
Labor Mix
Policy Experiments
Accounting Equations
Workforce Cap
Viewing Terminal Values
Labor Cap
Summary
4 The Growth of a Field
Overview
Background
Hypotheses
The Basic Diffusion Process
A Note on Behavior
Similar Models
The Adoption Process
Quality of Work
Software Tools
Conclusions
5 Capacity and Market Growth
Overview
Sales and Replacements
Production
Combining Sectors
Comparing Runs
Experimentation
6 Competitive Dynamics
Overview
Adding Subscripts to the Model
Demand and Delivery Delay
Conclusion
7 Financial Modeling and Risk
Overview
Accounting and Causality
Levels of Detail
An Investment Evaluation Model
Sales and Receipts
Equilibrium Initializations
The Complete Model
Sensitivity Testing
Displaying Sensitivity Results
Financial Modeling and Market Growth
Simulation Results
Sensitivity Tests
Conclusions
8 Furnaces, Pendulums and Oscillation
Overview
Thermostatic Control
Simulation
The Pendulum
Simulating the Pendulum
More on Runge-Kutta Integration
Conclusions on Integration Techniques
9 Discrete Functions
Overview
Continuous Versus Discrete Delays
Material and Information Delays
Conveyors
Initialization of Conveyors
Material in Conveyors
Population Example with Conveyors
Queues
QUEUES with Attributes
Batch Delays
10 Molecules
Overview
Getting and using the Molecules
Extending the Molecules
Appendix A Models that Come with Vensim
Overview
Modeling Guide Models
User's Guide Models
Sample Models
bpr
Extra
finance
kalman
maint1
market
mproject
urban
wrld3-91
Reference Manual
1 Introduction
Chapter Overview
User's Guide
Modeling Guide
Reference Manual
DSS Reference Supplement
Readme Notes
Version 5 Changes
Vensim Overview
General Navigation
Vensim Software
Vensim PLE
Vensim PLE Plus
Vensim Professional
Vensim DSS
Vensim Model Reader
Vensim DLL
Model Capacities
Publishing your Model
Computer Platforms
Macintosh Notes
Typographic Conventions
Mouse Movement Terminology
2 The Vensim Modeling Language
Overview
Mathematical Foundation
Integral and Differential Equations
Variable Types
Causal Models
Computational Sequence
Variables
Rules for Variable Names
Equations
Equation Components
Equation Format and Conventions
Operators
:NA:
Data Equations
Getting Data from Spreadsheets
Shifting Time Points
Subscripts
Multiple Equations
Subscripting Constants
Subscript Functions
Mixed Variables Types
Advanced Subscript Manipulation
Numeric Ranges
VECTOR ELM MAP
Subranges
Mapping of Subscript Ranges
Simulation Control Parameters
Special Variable Names
Acceptable Integration Errors
Alternative Time Bases
RC START TIME
Groups
Definition of Ranges
Macros
Defining Macros
Using Macros
3 Model Settings to Units Checking
Overview
Model Settings
Time Bounds
Info/Sketch
Units Equiv
Error Checking
Equation Editor
Text Editor
Error Checking Sequence
Syntax Errors and Incomplete Equations
Syntax Errors and the Text Editor
Syntax Errors in a .mdl File
Problems with Variable Types
Subscript Errors
Tracing Subscript Errors
Usage Messages
Not Defined
Multiple Equations
Simultaneous Equations
Subscripts and Simultaneous Equations
Fixing Simultaneous Equations
Iterative Solutions to Active Simultaneous Equations
Units Checking
Units Check Output
Source of Units Check Errors
Units and Lookup Functions
Correcting Units Errors
Reforming and Cleaning Models
4 Functions and Keywords
Overview
Summary List of Functions
Lookups
Using Lookups
Special Interpolation Modes
Functions A-D
A FUNCTION OF
ABS
ACTIVE INITIAL
ALLOCATE AVAILABLE
ALLOCATE BY PRIORITY
ALLOC P
ARCCOS
ARCSIN
ARCTAN
COS
COSH
CUMULATE
DELAY BATCH
DELAY CONVEYOR
DELAY FIXED
DELAY INFORMATION
DELAY MATERIAL
DELAY N
DELAY PROFILE
DELAY1
DELAY3
DELAYP
DEMAND AT PRICE
DEPRECIATE BY SCHEDULE
DEPRECIATE STRAIGHTLINE
Functions E-I
ELMCOUNT
EXP
FIND MARKET PRICE
FIND ZERO
FORECAST
GAME
GAMMA LN
GET 123 CONSTANTS
GET 123 DATA
GET 123 LOOKUPS
GET DATA AT TIME
GET DATA BETWEEN TIMES
GET DATA FIRST TIME
GET DATA LAST TIME
GET DATA MAX
GET DATA MEAN
GET DATA MIN
GET DATA STDV
GET DATA TOTAL POINTS
GET VDF CONSTANTS
GET VDF DATA
GET VDF LOOKUPS
GET XLS CONSTANTS
GET XLS DATA
GET XLS LOOKUPS
IF THEN ELSE
INITIAL
INTEG
INTEGER
INTERNAL RATE OF RETURN
INVERT MATRIX
Functions L-P
LN
LOG
LOOKUP AREA
LOOKUP BACKWARD
LOOKUP EXTRAPOLATE
LOOKUP FORWARD
LOOKUP INVERT
LOOKUP SLOPE
MARKETP
MAX
MESSAGE
MIN
MODULO
NET PRESENT VALUE
NPV
NPVE
POWER
PROD
PULSE
PULSE TRAIN
Functions P-R
QUANTUM
QUEUE AGE AVERAGE
QUEUE AGE IN RANGE
QUEUE AGE OLDEST
QUEUE ATTRIB AVERAGE
QUEUE ATTRIB IN RANGE
QUEUE ATTRIB MAX
QUEUE ATTRIB MIN
QUEUE ATTRIB QUANTITY
QUEUE FIFO
QUEUE FIFO ATTRIB
RAMP
RANDOM...
RC COMPARE
REINITIAL
Functions S-Z
SAMPLE IF TRUE
SHIFT IF TRUE
SIN
SINH
SINTEG
SMOOTH N
SMOOTH
SMOOTH3
SQRT
STEP
SUM
TABBED ARRAY
SUPPLY AT PRICE
TAN
TANH
TIME BASE
TIME SHIFT
TIME TRANSITION
TREND
VECTOR ELM MAP
VECTOR LOOKUP
VECTOR RANK
VECTOR REORDER
VECTOR SELECT
VECTOR SORT ORDER
VMAX
VMIN
WITH LOOKUP
X IF MISSING
XIDZ
ZIDZ
5 The Sketch Editor
Overview
Starting the Sketch Editor
Notes on Sketch Behavior
Models and Views
Sketches and Views
Sketches and Equations
Variables, Words and Arrows
The Edit Menu
The View Menu
The Layout Menu
Status Bar
The Sketch Layout
Defined Variables and Shadow Variables
Defined Variables
Shadow Variables
Sketch Comments, Valves and Junctions
Sketch Tools
Pointer
Variable Class
Arrow Class
Rate Class
Input Output Object
Sketch Comment
Existing Variable Class
Merge
Magic Wand
Delete
Equations Class
Building Sketches from Models
Changing the Appearance of a View
Moving a Word
Reshaping an Arrow
Reattaching an Arrow
Resizing a Box or Circle around a Word
Wrapping Text
Joining Words
Variable Word Options
Sketch Comment Options
Valve Options
Arrow Options
Editing Equations
Sketch Workbench Interactions
Variable Selection
Navigation
Tool Activation
Simulation
Free-Form Sketching
Sketching a Database
6 The Equation Editor