QwtScaleArithmetic Class Reference

Arithmetic including a tolerance. More...

#include <qwt_scale_engine.h>

List of all members.

Static Public Member Functions
static int	compareEps (double value1, double value2, double intervalSize)
	Compare 2 values, relative to an interval.
static double	ceilEps (double value, double intervalSize)
static double	floorEps (double value, double intervalSize)
static double	divideEps (double interval, double steps)
	Divide an interval into steps.
static double	ceil125 (double x)
static double	floor125 (double x)
	Find the largest value out of {1,2,5}*10^n with an integer number n which is smaller than or equal to x.

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Detailed Description

Arithmetic including a tolerance.

Definition at line 22 of file qwt_scale_engine.h.

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Member Function Documentation

double QwtScaleArithmetic::ceil125

(

double

x )

[static]

Find the smallest value out of {1,2,5}*10^n with an integer number n which is greater than or equal to x

Parameters:

x	Input value

Definition at line 98 of file qwt_scale_engine.cpp.

References QuadProgPP::pow(), and sign().

Referenced by QwtScaleEngine::divideInterval().

{
    if (x == 0.0) 
        return 0.0;

    const double sign = (x > 0) ? 1.0 : -1.0;
    const double lx = log10(fabs(x));
    const double p10 = floor(lx);
    
    double fr = pow(10.0, lx - p10);
    if (fr <=1.0)
       fr = 1.0; 
    else if (fr <= 2.0)
       fr = 2.0;
    else if (fr <= 5.0) 
       fr = 5.0;
    else
       fr = 10.0;

    return sign * fr * pow(10.0, p10);
}

double QwtScaleArithmetic::ceilEps	(	double	value,
		double	intervalSize
	)		[static]

Ceil a value, relative to an interval

Parameters:

value	Value to ceil
intervalSize	Interval size

See also:

floorEps()

Definition at line 50 of file qwt_scale_engine.cpp.

References _eps.

Referenced by QwtLinearScaleEngine::align().

{
    const double eps = _eps * intervalSize;

    value = (value - eps) / intervalSize;
    return ceil(value) * intervalSize;
}

int QwtScaleArithmetic::compareEps	(	double	value1,
		double	value2,
		double	intervalSize
	)		[static]

Compare 2 values, relative to an interval.

Values are "equal", when :

Parameters:

value1	First value to compare
value2	Second value to compare
intervalSize	interval size

Returns:

0: if equal, -1: if value2 > value1, 1: if value1 > value2

Definition at line 28 of file qwt_scale_engine.cpp.

References _eps, and qwtAbs.

Referenced by QwtScaleEngine::contains().

{
    const double eps = qwtAbs(_eps * intervalSize);

    if ( value2 - value1 > eps )
        return -1;

    if ( value1 - value2 > eps )
        return 1;

    return 0;
}

double QwtScaleArithmetic::divideEps	(	double	intervalSize,
		double	numSteps
	)		[static]

Divide an interval into steps.

Parameters:

intervalSize	Interval size
numSteps	Number of steps

Returns:

Step size

Definition at line 84 of file qwt_scale_engine.cpp.

References _eps.

Referenced by QwtScaleEngine::divideInterval().

{
    if ( numSteps == 0.0 || intervalSize == 0.0 )
        return 0.0;

    return (intervalSize - (_eps * intervalSize)) / numSteps;
} 

double QwtScaleArithmetic::floor125

(

double

x )

[static]

Find the largest value out of {1,2,5}*10^n with an integer number n which is smaller than or equal to x.

Parameters:

x	Input value

Definition at line 126 of file qwt_scale_engine.cpp.

References QuadProgPP::pow(), and sign().

{
    if (x == 0.0)
        return 0.0;

    double sign = (x > 0) ? 1.0 : -1.0;
    const double lx = log10(fabs(x));
    const double p10 = floor(lx);

    double fr = pow(10.0, lx - p10);
    if (fr >= 10.0)
       fr = 10.0;
    else if (fr >= 5.0)
       fr = 5.0;
    else if (fr >= 2.0)
       fr = 2.0;
    else
       fr = 1.0;

    return sign * fr * pow(10.0, p10);
}

double QwtScaleArithmetic::floorEps	(	double	value,
		double	intervalSize
	)		[static]

Floor a value, relative to an interval

Parameters:

value	Value to floor
intervalSize	Interval size

See also:

floorEps()

Definition at line 67 of file qwt_scale_engine.cpp.

References _eps.

Referenced by QwtLinearScaleEngine::align().

{
    const double eps = _eps * intervalSize;

    value = (value + eps) / intervalSize;
    return floor(value) * intervalSize;
}

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

• qwt_scale_engine.h
• qwt_scale_engine.cpp