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 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 deserialization 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, colour, 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...
 

Member Function Documentation

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

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, colour, thickness etc.

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

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.

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

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).

Reimplemented in chrono::ChFunction_Sequence, chrono::ChFunction_Recorder, chrono::ChFunction_Lambda< LAMBDA >, chrono::ChFunction_Fillet3, chrono::ChFunction_ConstAcc, chrono::ChFunction_Mocap, chrono::ChFunction_Sine, chrono::ChFunction_Poly345, chrono::ChFunction_Sigma, chrono::ChFunction_Ramp, chrono::ChFunction_Const, chrono::ChFunction_Poly, and chrono::ChFunction_Matlab.

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

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).

Reimplemented in chrono::ChFunction_Sequence, chrono::ChFunction_Recorder, chrono::ChFunction_Lambda< LAMBDA >, chrono::ChFunction_Fillet3, chrono::ChFunction_ConstAcc, chrono::ChFunction_Mocap, chrono::ChFunction_Sine, chrono::ChFunction_Poly345, chrono::ChFunction_Sigma, chrono::ChFunction_Ramp, chrono::ChFunction_Const, chrono::ChFunction_Poly, and chrono::ChFunction_Matlab.

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

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.