  We present a new method implemented in our new package \textit{FitAik}, to
perform least-squares fitting of calculated and experimental atomic transition
probabilities, by using the mono-electronic transition integrals $\langle n\ell
|r| n'\ell' \rangle$ (with $r$ the electronic radial coordinate) as adjustable
quantities. \textit{FitAik} is interfaced to the Cowan suite of codes, for
which it automatically writes input files and reads output files. We illustrate
our procedure with the example of Er$^{+}$ ion, for which the agreement between
calculated and experimental Einstein coefficients is found to be very good. The
source code of \emph{FitAik} can be found on GitLab, and the calculated
Einstein coefficients are stored in our new database CaDDiACs. They are also
used to calculate the dynamic dipole polarizability of Er$^+$.
