Class OffsetLinearScale
- All Implemented Interfaces:
Serializable
,Scale
A Scale for linear transformations with an offset that has to be applied first when converting to the standard (SI) unit, before the scaling takes place, e.g. for Temperature. As an example, transform from Degrees Fahrenheit to Kelvin (SI). The conversion is K = (F + 459.67) × 5⁄9, and F = K × 9⁄5 − 459.67.
When we have an original scale with offset o1 and scalefactor f1, the calculation to the base unit is
valueSI = (value1 + o1) * f1
So the offset is expressed in the "unit" of the value. As an example, when we transform degrees Fahrenheit to Kelvin, the factor is 5/9, and the offset is 459.67 (degrees Fahrenheit of 0 degrees Fahrenheit expressed in Kelvin). The formula becomes: K = (F + 459.67) * 5/9. So 0 F is 459.67 * 5/9 = 255.372 K. For Celcius to Kelvin, the scale factor is 1, and the offset 273.15. From Fahrenheit to Celcius, the offset is -32, and the factor is 5/9.
When we apply a second offset transformation on a scale, e.g. from Fahrenheit to Celcius to Kelvin, this works as follows: If we combine a second scale factor for a derived unit with offset o2 and scalefactor f2, we need to calculate the ultimate scale to the base (si) unit. The factor then becomes:
value1 = (value2 + o2) * f2 valueSI = (value1 + o1) * f1 = value2 * (f1 * f2) + (f1 * f2 * o2 + f1 * o1)
as an example for F --2--> C --1--> K: o1 = 273.15, f1 = 1, o2 = -32, f2 = 5/9:
110 F = 110*5/9 -32*5/9 + 273.15 = 316.483 K.
Copyright (c) 2013-2024 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved.
BSD-style license. See DJUNITS License.
- Author:
- Alexander Verbraeck, Peter Knoppers
- See Also:
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Constructor Summary
ConstructorDescriptionOffsetLinearScale
(double conversionFactorToStandardUnit, double offsetToStandardUnit) Construct a Scale for linear transformations with an offset, e.g. for Temperature. -
Method Summary
Modifier and TypeMethodDescriptionboolean
final double
fromStandardUnit
(double value) Convert a value from an SI value to a value in the unit that uses this scale.final double
Retrieve the offset from the standard unit.int
hashCode()
boolean
Return whether a scale is a 'standard' scale that would belong to an SI unit.final double
toStandardUnit
(double value) Convert a value to an SI value using this scale.toString()
Methods inherited from class org.djunits.unit.scale.LinearScale
getConversionFactorToStandardUnit
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Constructor Details
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OffsetLinearScale
public OffsetLinearScale(double conversionFactorToStandardUnit, double offsetToStandardUnit) Construct a Scale for linear transformations with an offset, e.g. for Temperature.- Parameters:
conversionFactorToStandardUnit
- double; the conversion factor by which this number has to be multiplied to convert it to the standard (e.g., SI) unit.offsetToStandardUnit
- the offset that has to be taken into account for conversions; when converting to a standard unit, the offset is applied first.
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Method Details
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toStandardUnit
public final double toStandardUnit(double value) Description copied from interface:Scale
Convert a value to an SI value using this scale.- Specified by:
toStandardUnit
in interfaceScale
- Overrides:
toStandardUnit
in classLinearScale
- Parameters:
value
- double; the value to convert- Returns:
- the corresponding SI value
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fromStandardUnit
public final double fromStandardUnit(double value) Description copied from interface:Scale
Convert a value from an SI value to a value in the unit that uses this scale.- Specified by:
fromStandardUnit
in interfaceScale
- Overrides:
fromStandardUnit
in classLinearScale
- Parameters:
value
- double; the value to convert- Returns:
- the corresponding value in the given unit
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getOffsetToStandardUnit
public final double getOffsetToStandardUnit()Retrieve the offset from the standard unit.- Returns:
- double; the offset from the standard unit
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isBaseSIScale
public boolean isBaseSIScale()Description copied from interface:Scale
Return whether a scale is a 'standard' scale that would belong to an SI unit. For a linear scale, any scale with conversion factor 1 would be considered standard. For an offset scale, it would be considered standard if the offset is 0 and the conversion factor is 1.- Specified by:
isBaseSIScale
in interfaceScale
- Overrides:
isBaseSIScale
in classLinearScale
- Returns:
- boolean; whether the scale is a 'standard' scale that would belong to an SI unit.
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hashCode
public int hashCode()- Overrides:
hashCode
in classLinearScale
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equals
- Overrides:
equals
in classLinearScale
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toString
- Overrides:
toString
in classLinearScale
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