# cfdm.rtol¶

cfdm.rtol(*rtol)[source]

The tolerance on relative differences when testing for numerically tolerant equality.

Two real numbers x and y are considered equal if abs(x-y) <= atol + rtol*abs(y), where atol (the tolerance on absolute differences) and rtol (the tolerance on relative differences) are positive, typically very small numbers. By default both are set to the system epsilon (the difference between 1 and the least value greater than 1 that is representable as a float).

New in version (cfdm): 1.7.0

Parameters
rtol: float, optional

The new value of relative tolerance. The default is to not change the current value.

Returns
float

The value prior to the change, or the current value if no new value was specified.

Examples:

>>> rtol()
2.220446049250313e-16
>>> old = rtol(1e-10)
>>> rtol()
1e-10
>>> rtol(old)
1e-10
>>> rtol()
2.220446049250313e-16