# LogQuantity¶

class astropy.units.LogQuantity[source]

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(self[, n, axis]) ediff1d(self[, to_end, to_begin]) ptp([axis, out, keepdims]) 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(self, n=1, axis=-1)[source]
ediff1d(self, to_end=None, to_begin=None)[source]
ptp(axis=None, out=None, keepdims=False)[source]

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

Refer to numpy.ptp for full documentation.

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

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

Refer to numpy.std for full documentation.

numpy.std
var(axis=None, dtype=None, out=None, ddof=0, keepdims=False)[source]
Refer to numpy.var for full documentation.
numpy.var