# FilterFunction

`class boulderopal.noise_reconstruction.FilterFunction(frequencies, inverse_powers, uncertainties=None)`

A class to store information about the controls applied in the noise reconstruction process, in the form of filter functions.

The filter function specifies how sensitive a set of controls is to a specific
noise, at a certain frequency. Filter functions can be calculated using
the `execute_graph`

function together with the `graph.filter_function`

operator. The output of that operation can then be passed directly to this
function.

### Parameters

**frequencies**(*np.ndarray*) – A 1D array of the frequencies where the filter function is sampled. The frequencies must be provided in ascending order.**inverse_powers**(*np.ndarray*) – A 1D arrays of the values of the filter function at the frequencies where it is sampled. Must have the same length as frequencies, and all its values must be greater or equal to zero.**uncertainties**(*np.ndarray**or**None**,**optional*) – The uncertainties associated with each sampled point of the filter function. These values are not used for noise reconstruction.