  Theoretical analysis typically involves imaginary-time correlation functions.
Inferring real-time dynamical response functions from this information is
notoriously difficult. However, as we articulate here, it is straightforward to
compute imaginary-time correlators from the measured frequency dependence of
(real-time) response functions. In addition to facilitating comparison between
theory and experiment, the proposed approach can be useful in extracting
certain aspects of the (long-time relaxational) dynamics from a complex data
set. We illustrate this with an analysis of the nematic response inferred from
Raman scattering spectroscopy on the iron-based superconductor
Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$, which includes a new method for identifying a
putative quantum critical contribution to that response.
