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DynamicSystems[SystemOptions] - query and change default options

Calling Sequence

SystemOptions( arg1, arg2, ... )


SystemOptions( reset )




argument of the form name or name=val



The SystemOptions command is a mechanism for querying and setting the default values of options used by the commands of DynamicSystems package.


An argument of the form name = val specifies the setting for the named variable.

For each argument of this type, SystemOptions returns the prior value of the variable.


If an argument is a name, then the current value of the named variable is returned as the function value.


If called with many arguments, SystemOptions returns an expression sequence containing the values.


If called with no arguments, SystemOptions returns a sequence of all the options and their current values.


If called with the single argument reset, SystemOptions resets all settings to their built-in values and returns a sequence of equations of the form name = val, where val is the built-in value of name.

Global Variables


The DynamicSystems package uses several global variables that must be unassigned. The actual variables used can be modified or queried by calling SystemOptions with the appropriate option. For example, SystemOptions('continuoustimevar' = T) changes the variable used for continuous-time to T (the default is t).


The following table lists the default variables, their meaning, and the associated option





discrete time



complex frequency



continuous time












discrete frequency


Option Description and Default Values


cancellation = truefalse

The default value for the option cancellation, which determines whether pole-zero cancellation is applied to the transfer function of a system during creation. The default is false.


colors = list( name )

The color sequence used to draw plots with multiple colors. The default is [RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN].


complexfreqvar = symbol

The complex frequency variable used to describe continuous systems as transfer functions. The default is s. See discretefreqvar.


conjugate = truefalse

The default value for the option conjugate, which determines whether the complex conjugates of complex roots of a ZPK model are automatically added during system creation. The default is false.


continuoustimevar = symbol

The default continuous-time variable used to describe continuous-time state-space and differential equation systems. The default is t. See discretetimevar.


decibels = truefalse

The default value for the option decibels, which selects the units of gain. The value true selects decibels, the value false selects linear gain. The default is true.


discrete = truefalse

The default value for the option discrete, which determines whether a system is discrete or continuous. The default is false.


discretefreqvar = symbol

The discrete complex frequency variable used to describe discrete systems as transfer functions. The default is z. See complexfreqvar.


discretetimevar = symbol

The default discrete-time index variable used to describe discrete-time state-space and difference equation systems. The default is q. See continuoustimevar.


duration = positive

The default duration of the DynamicSystems[ResponsePlot] command. The default is 10.0.


hertz = truefalse

The default value for the option hertz, which is used by the plot commands to select the unit of frequency. The value true selects hertz (cycles/second), the value false selects radians/second. The default is false.


inputvariable = symbol

The base name used to generate input variables. The generated names include appended integers. The default is u.


linearsolvemethod = none or solve

The method used by LinearAlgebra:-LinearSolve when computing a transfer function from a system matrix. The solve method is more efficient for some systems. The default is none.


outputvariable = symbol

The base name used to generate output variables. The generated names include appended integers. The default is y.


parameters = set( name = complexcons ) or list( name = complexcons )

Specifies numeric values of parameters. Procedures that require numeric values, primarily plot and simulation routines, substitute the numeric value on the right side of each equation for the name on the left side in the model parameters. The default is the empty set.


radians = truefalse

The default value for the option radians, which selects the units for phase. The value true selects radians, the value false selects degrees. The default is false.


relativeerror = nonnegative number

The default value for the option relativeerror, which is used by various procedures to determine how close roots must be to be considered equal. The default is 0.001.


samplecount = posint

The default value for the option samplecount, which selects the number of samples of a discrete system. The default value is 10.


sampletime = positive number

The default value for the option sampletime, which is used to select the sample time (period) of discrete systems. The default is 1.


statevariable = symbol

The base name used to generate state variables. The generated symbols include appended integers. The default is x.



Return a sequence of all options and their values.




Return the value of the statevariable option.




Reassign statevariable, the global variable that denotes states of a system, and return its prior value.







Reset all options to their original values and return the sequence of names and values.




See Also


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