FGTable Class Reference

#include <FGTable.h>

Detailed Description

Models a one, two, or three dimensional lookup table for use in aerodynamics and function definitions.

For a single "vector" lookup table, the format is as follows:

<table name="property_name">
  <independentVar lookup="row"> property_name </independentVar>
  <tableData>
    key_1 value_1
    key_2 value_2
    ...  ...
    key_n value_n
  </tableData>
</table>

The lookup="row" attribute in the independentVar element is option in this case; it is assumed that the independentVar is a row variable.

A "real life" example is as shown here:

<table>
  <independentVar lookup="row"> aero/alpha-rad </independentVar>
  <tableData>
   -1.57  1.500
   -0.26  0.033
    0.00  0.025
    0.26  0.033
    1.57  1.500
  </tableData>
</table>

The first column in the data table represents the lookup index (or "key"). In this case, the lookup index is aero/alpha-rad (angle of attack in radians). If alpha is 0.26 radians, the value returned from the lookup table would be 0.033.

The definition for a 2D table, is as follows:

<table name="property_name">
  <independentVar lookup="row"> property_name </independentVar>
  <independentVar lookup="column"> property_name </independentVar>
  <tableData>
                {col_1_key   col_2_key   ...  col_n_key }
    {row_1_key} {col_1_data  col_2_data  ...  col_n_data}
    {row_2_key} {...         ...         ...  ...       }
    { ...     } {...         ...         ...  ...       }
    {row_n_key} {...         ...         ...  ...       }
  </tableData>
</table>

The data is in a gridded format.

A "real life" example is as shown below. Alpha in radians is the row lookup (alpha breakpoints are arranged in the first column) and flap position in degrees is

<table>
  <independentVar lookup="row">aero/alpha-rad</independentVar>
  <independentVar lookup="column">fcs/flap-pos-deg</independentVar>
  <tableData>
                0.0         10.0        20.0         30.0
    -0.0523599  8.96747e-05 0.00231942  0.0059252    0.00835082
    -0.0349066  0.000313268 0.00567451  0.0108461    0.0140545
    -0.0174533  0.00201318  0.0105059   0.0172432    0.0212346
     0.0        0.0051894   0.0168137   0.0251167    0.0298909
     0.0174533  0.00993967  0.0247521   0.0346492    0.0402205
     0.0349066  0.0162201   0.0342207   0.0457119    0.0520802
     0.0523599  0.0240308   0.0452195   0.0583047    0.0654701
     0.0698132  0.0333717   0.0577485   0.0724278    0.0803902
     0.0872664  0.0442427   0.0718077   0.088081     0.0968405
  </tableData>
</table>

The definition for a 3D table in a coefficient would be (for example):

<table name="property_name">
  <independentVar lookup="row"> property_name </independentVar>
  <independentVar lookup="column"> property_name </independentVar>
  <tableData breakpoint="table_1_key">
                {col_1_key   col_2_key   ...  col_n_key }
    {row_1_key} {col_1_data  col_2_data  ...  col_n_data}
    {row_2_key} {...         ...         ...  ...       }
    { ...     } {...         ...         ...  ...       }
    {row_n_key} {...         ...         ...  ...       }
  </tableData>
  <tableData breakpoint="table_2_key">
                {col_1_key   col_2_key   ...  col_n_key }
    {row_1_key} {col_1_data  col_2_data  ...  col_n_data}
    {row_2_key} {...         ...         ...  ...       }
    { ...     } {...         ...         ...  ...       }
    {row_n_key} {...         ...         ...  ...       }
  </tableData>
  ...
  <tableData breakpoint="table_n_key">
                {col_1_key   col_2_key   ...  col_n_key }
    {row_1_key} {col_1_data  col_2_data  ...  col_n_data}
    {row_2_key} {...         ...         ...  ...       }
    { ...     } {...         ...         ...  ...       }
    {row_n_key} {...         ...         ...  ...       }
  </tableData>
</table>

[Note the "breakpoint" attribute in the tableData element, above.]

Here's an example:

<table>
  <independentVar lookup="row">fcs/row-value</independentVar>
  <independentVar lookup="column">fcs/column-value</independentVar>
  <independentVar lookup="table">fcs/table-value</independentVar>
  <tableData breakPoint="-1.0">
           -1.0     1.0
    0.0     1.0000  2.0000
    1.0     3.0000  4.0000
  </tableData>
  <tableData breakPoint="0.0000">
            0.0     10.0
    2.0     1.0000  2.0000
    3.0     3.0000  4.0000
  </tableData>
  <tableData breakPoint="1.0">
           0.0     10.0     20.0
     2.0   1.0000   2.0000   3.0000
     3.0   4.0000   5.0000   6.0000
    10.0   7.0000   8.0000   9.0000
  </tableData>
</table>

In addition to using a Table for something like a coefficient, where all the row and column elements are read in from a file, a Table could be created and populated completely within program code:

// First column is thi, second is neta (combustion efficiency)
Lookup_Combustion_Efficiency = new FGTable(12);

*Lookup_Combustion_Efficiency << 0.00 << 0.980;
*Lookup_Combustion_Efficiency << 0.90 << 0.980;
*Lookup_Combustion_Efficiency << 1.00 << 0.970;
*Lookup_Combustion_Efficiency << 1.05 << 0.950;
*Lookup_Combustion_Efficiency << 1.10 << 0.900;
*Lookup_Combustion_Efficiency << 1.15 << 0.850;
*Lookup_Combustion_Efficiency << 1.20 << 0.790;
*Lookup_Combustion_Efficiency << 1.30 << 0.700;
*Lookup_Combustion_Efficiency << 1.40 << 0.630;
*Lookup_Combustion_Efficiency << 1.50 << 0.570;
*Lookup_Combustion_Efficiency << 1.60 << 0.525;
*Lookup_Combustion_Efficiency << 2.00 << 0.345;

The first column in the table, above, is thi (the lookup index, or key). The second column is the output data - in this case, "neta" (the Greek letter referring to combustion efficiency). Later on, the table is used like this:

combustion_efficiency = Lookup_Combustion_Efficiency->GetValue(equivalence_ratio);

Author:: Jon S. Berndt

Version:

Id: FGTable.h,v 1.8 2007/02/25 13:52:57 jberndt Exp

Definition at line 244 of file FGTable.h.


Public Member Functions
	FGTable (int)
	FGTable (FGPropertyManager propMan, Element el)
	The constructor for a table.
	FGTable (const FGTable &table)
	This is the very important copy constructor.
double	GetElement (int r, int c, int t)
double	GetElement (int r, int c)
double	GetValue (double rowKey, double colKey, double TableKey) const
double	GetValue (double rowKey, double colKey) const
double	GetValue (double key) const
double	GetValue (void) const
FGTable &	operator<< (const int n)
FGTable &	operator<< (const double n)
void	operator<< (stringstream &)
	Read the table in.
void	Print (void)
void	SetColumnIndexProperty (FGPropertyManager *node)
void	SetRowIndexProperty (FGPropertyManager *node)
	~FGTable ()
	Destructor.

Constructor & Destructor Documentation

FGTable ( const FGTable & table )

Parameters:

table

a const reference to a table.

Definition at line 67 of file FGTable.cpp.

Member Function Documentation

void operator<< ( stringstream & in_stream )

Data in the config file should be in matrix format with the row independents as the first column and the column independents in the first row. The implication of this layout is that there should be no value in the upper left corner of the matrix e.g:

           0  10  20 30 ...
      -5   1  2   3  4  ...
       ...

For multiple-table (i.e. 3D) data sets there is an additional number key in the table definition. For example:

       0.0
           0  10  20 30 ...
      -5   1  2   3  4  ...
       ...

Definition at line 469 of file FGTable.cpp.

The documentation for this class was generated from the following files:

FGTable Class Reference

Detailed Description

Public Member Functions

Constructor & Destructor Documentation

Member Function Documentation