chrono::ChFunction Class Referenceabstract

## Description

Interface base class for scalar functions of the type: y= f(x)

The ChFunction class defines the base class for all Chrono functions of type y=f(x), that is scalar functions of an input variable x (usually, the time). ChFunctions are often used to set time-dependent properties, for example to set motion laws in linear actuators, engines, etc. This base class just represent a constant function of the type y= C. Inherited classes must override at least the Get_y() method, in order to represent more complex functions.

#include <ChFunction_Base.h>

Inheritance diagram for chrono::ChFunction:

## Public Types

enum  FunctionType {
FUNCT_CUSTOM, FUNCT_CONST, FUNCT_CONSTACC, FUNCT_DERIVE,
FUNCT_FILLET3, FUNCT_INTEGRATE, FUNCT_MATLAB, FUNCT_MIRROR,
FUNCT_MOCAP, FUNCT_NOISE, FUNCT_OPERATION, FUNCT_OSCILLOSCOPE,
FUNCT_POLY, FUNCT_POLY345, FUNCT_RAMP, FUNCT_RECORDER,
FUNCT_REPEAT, FUNCT_SEQUENCE, FUNCT_SIGMA, FUNCT_SINE,
FUNCT_LAMBDA
}
Enumeration of function types.

## Public Member Functions

ChFunction (const ChFunction &other)

virtual ChFunctionClone () const =0
"Virtual" copy constructor.

virtual FunctionType Get_Type () const
Return the unique function type identifier.

virtual double Get_y (double x) const =0
Return the y value of the function, at position x.

virtual double Get_y_dx (double x) const
Return the dy/dx derivative of the function, at position x. More...

virtual double Get_y_dxdx (double x) const
Return the ddy/dxdx double derivative of the function, at position x. More...

virtual double Get_weight (double x) const
Return the weight of the function (useful for applications where you need to mix different weighted ChFunctions)

virtual void Estimate_x_range (double &xmin, double &xmax) const
Return an estimate of the range of the function argument. More...

virtual void Estimate_y_range (double xmin, double xmax, double &ymin, double &ymax, int derivate) const
Return an estimate of the range of the function value. More...

virtual double Get_y_dN (double x, int derivate) const
Return the function derivative of specified order at the given point. More...

virtual void Update (const double x)
Update could be implemented by children classes, ex. to launch callbacks.

virtual double Compute_max (double xmin, double xmax, double sampling_step, int derivate) const
Compute the maximum of y(x) in a range xmin-xmax, using a sampling method.

virtual double Compute_min (double xmin, double xmax, double sampling_step, int derivate) const
Compute the minimum of y(x) in a range xmin-xmax, using a sampling method.

virtual double Compute_mean (double xmin, double xmax, double sampling_step, int derivate) const
Compute the mean value of y(x) in a range xmin-xmax, using a sampling method.

virtual double Compute_sqrmean (double xmin, double xmax, double sampling_step, int derivate) const
Compute the square mean val. of y(x) in a range xmin-xmax, using sampling.

virtual double Compute_int (double xmin, double xmax, double sampling_step, int derivate) const
Compute the integral of y(x) in a range xmin-xmax, using a sampling method.

virtual double Get_Ca_pos () const
Computes the positive acceleration coefficient (inherited classes should customize this).

virtual double Get_Ca_neg () const
Compute the positive acceleration coefficient (inherited classes should customize this).

virtual double Get_Cv () const
Compute the speed coefficient (inherited classes must customize this).

virtual int HandleNumber () const
Return the number of handles of the function.

virtual bool HandleAccess (int handle_id, double mx, double my, bool set_mode)
Get the x and y position of handle, given identifier. More...

virtual void ArchiveOUT (ChArchiveOut &marchive)
Method to allow serialization of transient data to archives.

virtual void ArchiveIN (ChArchiveIn &marchive)
Method to allow de-serialization of transient data from archives. More...

virtual int FilePostscriptPlot (ChFile_ps *m_file, int plotY, int plotDY, int plotDDY)
Plot function in graph space of the ChFile_ps postscript file where zoom factor, centering, color, thickness etc. More...

virtual int FileAsciiPairsSave (ChStreamOutAscii &m_file, double xmin=0, double xmax=1, int msamples=200)
Save function as X-Y pairs separated by space, with CR at each pair, into an ASCII file. More...

## ◆ ArchiveIN()

 void chrono::ChFunction::ArchiveIN ( ChArchiveIn & marchive )
virtual

Method to allow de-serialization of transient data from archives.

Method to allow de serialization of transient data from archives.

## ◆ Estimate_x_range()

 virtual void chrono::ChFunction::Estimate_x_range ( double & xmin, double & xmax ) const
inlinevirtual

Return an estimate of the range of the function argument.

(Can be used for automatic zooming in a GUI)

## ◆ Estimate_y_range()

 void chrono::ChFunction::Estimate_y_range ( double xmin, double xmax, double & ymin, double & ymax, int derivate ) const
virtual

Return an estimate of the range of the function value.

(Can be used for automatic zooming in a GUI)

 int chrono::ChFunction::FileAsciiPairsSave ( ChStreamOutAscii & m_file, double xmin = 0, double xmax = 1, int msamples = 200 )
virtual

Save function as X-Y pairs separated by space, with CR at each pair, into an ASCII file.

The output file can be later loaded into Excel, GnuPlot or other tools. The function is 'sampled' for nsteps times, from xmin to xmax.

## ◆ FilePostscriptPlot()

 int chrono::ChFunction::FilePostscriptPlot ( ChFile_ps * m_file, int plotY, int plotDY, int plotDDY )
virtual

Plot function in graph space of the ChFile_ps postscript file where zoom factor, centering, color, thickness etc.

are already defined. If plotDY=true, plots also the derivative, etc.

## ◆ Get_y_dN()

 double chrono::ChFunction::Get_y_dN ( double x, int derivate ) const
virtual

Return the function derivative of specified order at the given point.

Note that only order = 0, 1, or 2 is supported.

## ◆ Get_y_dx()

 virtual double chrono::ChFunction::Get_y_dx ( double x ) const
inlinevirtual

Return the dy/dx derivative of the function, at position x.

Note that inherited classes may also avoid overriding this method, because this base method already provide a general-purpose numerical differentiation to get dy/dx only from the Get_y() function. (however, if the analytical derivative is known, it may better to implement a custom method).

## ◆ Get_y_dxdx()

 virtual double chrono::ChFunction::Get_y_dxdx ( double x ) const
inlinevirtual

Return the ddy/dxdx double derivative of the function, at position x.

Note that inherited classes may also avoid overriding this method, because this base method already provide a general-purpose numerical differentiation to get ddy/dxdx only from the Get_y() function. (however, if the analytical derivative is known, it may be better to implement a custom method).

## ◆ HandleAccess()

 virtual bool chrono::ChFunction::HandleAccess ( int handle_id, double mx, double my, bool set_mode )
inlinevirtual

Get the x and y position of handle, given identifier.

If set mode, x and y values are stored. Return false if handle not found.

Reimplemented in chrono::ChFunction_Sequence.

The documentation for this class was generated from the following files:
• /builds/uwsbel/chrono/src/chrono/motion_functions/ChFunction_Base.h
• /builds/uwsbel/chrono/src/chrono/motion_functions/ChFunction_Base.cpp