Coordinates tranformations¶
QwtTransform¶
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class
qwt.transform.QwtTransform[source]¶ A transformation between coordinate systems
QwtTransform manipulates values, when being mapped between the scale and the paint device coordinate system.
A transformation consists of 2 methods:
- transform
- invTransform
where one is is the inverse function of the other.
When p1, p2 are the boundaries of the paint device coordinates and s1, s2 the boundaries of the scale, QwtScaleMap uses the following calculations:
p = p1 + (p2 - p1) * ( T(s) - T(s1) / (T(s2) - T(s1)) ) s = invT( T(s1) + ( T(s2) - T(s1) ) * (p - p1) / (p2 - p1) )
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bounded(value)[source]¶ Modify value to be a valid value for the transformation. The default implementation does nothing.
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transform(value)[source]¶ Transformation function
Parameters: value (float) – Value Returns: Modified value See also
QwtNullTransform¶
QwtLogTransform¶
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class
qwt.transform.QwtLogTransform[source]¶ Logarithmic transformation
QwtLogTransform modifies the values using numpy.log() and numpy.exp().
Note
In the calculations of QwtScaleMap the base of the log function has no effect on the mapping. So QwtLogTransform can be used for logarithmic scale in base 2 or base 10 or any other base.
Extremum values:
- QwtLogTransform.LogMin: Smallest allowed value for logarithmic scales: 1.0e-150
- QwtLogTransform.LogMax: Largest allowed value for logarithmic scales: 1.0e150
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bounded(value)[source]¶ Modify value to be a valid value for the transformation.
Parameters: value (float) – Value to be bounded Returns: Value unmodified
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transform(value)[source]¶ Transformation function
Parameters: value (float) – Value Returns: Modified value See also
QwtPowerTransform¶
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class
qwt.transform.QwtPowerTransform(exponent)[source]¶ A transformation using numpy.pow()
QwtPowerTransform preserves the sign of a value. F.e. a transformation with a factor of 2 transforms a value of -3 to -9 and v.v. Thus QwtPowerTransform can be used for scales including negative values.
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transform(value)[source]¶ Transformation function
Parameters: value (float) – Value Returns: Modified value See also
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class
qwt.transform.QwtTransform[source] A transformation between coordinate systems
QwtTransform manipulates values, when being mapped between the scale and the paint device coordinate system.
A transformation consists of 2 methods:
- transform
- invTransform
where one is is the inverse function of the other.
When p1, p2 are the boundaries of the paint device coordinates and s1, s2 the boundaries of the scale, QwtScaleMap uses the following calculations:
p = p1 + (p2 - p1) * ( T(s) - T(s1) / (T(s2) - T(s1)) ) s = invT( T(s1) + ( T(s2) - T(s1) ) * (p - p1) / (p2 - p1) )
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bounded(value)[source] Modify value to be a valid value for the transformation. The default implementation does nothing.
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transform(value)[source] Transformation function
Parameters: value (float) – Value Returns: Modified value See also
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invTransform(value)[source] Inverse transformation function
Parameters: value (float) – Value Returns: Modified value See also
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copy()[source] Returns: Clone of the transformation The default implementation does nothing.
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class
qwt.transform.QwtLogTransform[source] Logarithmic transformation
QwtLogTransform modifies the values using numpy.log() and numpy.exp().
Note
In the calculations of QwtScaleMap the base of the log function has no effect on the mapping. So QwtLogTransform can be used for logarithmic scale in base 2 or base 10 or any other base.
Extremum values:
- QwtLogTransform.LogMin: Smallest allowed value for logarithmic scales: 1.0e-150
- QwtLogTransform.LogMax: Largest allowed value for logarithmic scales: 1.0e150
-
bounded(value)[source] Modify value to be a valid value for the transformation.
Parameters: value (float) – Value to be bounded Returns: Value unmodified
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transform(value)[source] Transformation function
Parameters: value (float) – Value Returns: Modified value See also
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invTransform(value)[source] Inverse transformation function
Parameters: value (float) – Value Returns: Modified value See also
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copy()[source] Returns: Clone of the transformation
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class
qwt.transform.QwtPowerTransform(exponent)[source] A transformation using numpy.pow()
QwtPowerTransform preserves the sign of a value. F.e. a transformation with a factor of 2 transforms a value of -3 to -9 and v.v. Thus QwtPowerTransform can be used for scales including negative values.
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transform(value)[source] Transformation function
Parameters: value (float) – Value Returns: Modified value See also
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invTransform(value)[source] Inverse transformation function
Parameters: value (float) – Value Returns: Modified value See also
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copy()[source] Returns: Clone of the transformation
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