LogQuantity

class astropy.units.LogQuantity[source] [edit on github]

Bases: astropy.units.function.FunctionQuantity

A representation of a (scaled) logarithm of a number with a unit

Parameters:

value : number, Quantity, LogQuantity, or sequence of convertible items.

The numerical value of the logarithmic quantity. If a number or a Quantity with a logarithmic unit, it will be converted to unit and the physical unit will be inferred from unit. If a Quantity with just a physical unit, it will converted to the logarithmic unit, after, if necessary, converting it to the physical unit inferred from unit.

unit : string, UnitBase or FunctionUnitBase instance, optional

For an FunctionUnitBase instance, the physical unit will be taken from it; for other input, it will be inferred from value. By default, unit is set by the subclass.

dtype : dtype, optional

The dtype of the resulting Numpy array or scalar that will hold the value. If not provided, is is determined automatically from the input value.

copy : bool, optional

If True (default), then the value is copied. Otherwise, a copy will only be made if __array__ returns a copy, if value is a nested sequence, or if a copy is needed to satisfy an explicitly given dtype. (The False option is intended mostly for internal use, to speed up initialization where a copy is known to have been made. Use with care.)

Examples

Typically, use is made of an FunctionQuantity subclass, as in:

>>> import astropy.units as u
>>> u.Magnitude(-2.5)
<Magnitude -2.5 mag>
>>> u.Magnitude(10.*u.count/u.second)
<Magnitude -2.5 mag(ct / s)>
>>> u.Decibel(1.*u.W, u.DecibelUnit(u.mW))  
<Decibel 30. dB(mW)>

Methods Summary

diff([n, axis])
ediff1d([to_end, to_begin])
ptp([axis, out]) Peak to peak (maximum - minimum) value along a given axis.
std([axis, dtype, out, ddof, keepdims]) Returns the standard deviation of the array elements along given axis.
var([axis, dtype, out, ddof, keepdims]) Returns the variance of the array elements, along given axis.

Methods Documentation

diff(n=1, axis=-1)[source] [edit on github]
ediff1d(to_end=None, to_begin=None)[source] [edit on github]
ptp(axis=None, out=None)[source] [edit on github]

Peak to peak (maximum - minimum) value along a given axis.

Refer to numpy.ptp for full documentation.

See also

numpy.ptp
equivalent function
std(axis=None, dtype=None, out=None, ddof=0, keepdims=False)[source] [edit on github]

Returns the standard deviation of the array elements along given axis.

Refer to numpy.std for full documentation.

See also

numpy.std
equivalent function
var(axis=None, dtype=None, out=None, ddof=0, keepdims=False)[source] [edit on github]

Returns the variance of the array elements, along given axis.

Refer to numpy.var for full documentation.

See also

numpy.var
equivalent function