LogQuantity

class astropy.units.LogQuantity(value, unit=None, dtype=<class 'numpy.inexact'>, copy=True, order=None, subok=False, ndmin=0)

Bases: FunctionQuantity

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

Parameters:

valuenumber, Quantity, LogQuantity, or sequence of quantity-like.

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.

unitstr, UnitBase, or FunctionUnitBase, 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.

dtypedtype, 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.

copybool, 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, keepdims])	Peak to peak (maximum - minimum) value along a given axis.
std([axis, dtype, out, ddof, keepdims, where])	Returns the standard deviation of the array elements along given axis.
var([axis, dtype, out, ddof, keepdims, where])	Returns the variance of the array elements, along given axis.

Methods Documentation

diff(n=1, axis=-1)

ediff1d(to_end=None, to_begin=None)

ptp(axis=None, out=None, keepdims=False)

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, *, where=True)

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, *, where=True)

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

Refer to numpy.var for full documentation.

See also

numpy.var

equivalent function