In this paper, we present a direct method to obtain a set of curves that reproduce the observed variability of a ReRAM device. We have assumed a model in the flux-charge space, instead of the conventional current-voltage paradigm, because this allows us to use a very simple model that accurately reproduces the observed behavior. Thereby, we have observed that the extracted parameters of this model are correlated and with the help of this correlation, we can generate new parameter sets that have the same correlations, thus obtaining an accurate estimation of possible new resistive switching curves.