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| 1 | We propose a strategy to infer the transition redshift zda, which characterizes the passage through the universe decelerated to accelerated phases, in the framework f(R) gravities. To this end, we numerically reconstruct f(z), i. e. the corresponding f(R) function re-expressed in terms of the redshift z and we show how to match f(z) with cosmography. In particular, we relate f(z) and its derivatives to the cosmographic coefficients, i. e. H0, q0 and j0 and demonstrate that its corresponding evolution may be framed by means of an effective logarithmic dark energy term ΩX, slightly departing from the case of a pure cosmological constant. Afterwards, we show that our model predicts viable transition redshift constraints, which agree with ΛCDM. To do so, we compute the corresponding zda in terms of cosmographic outcomes and find that zda ≤ 1. Finally, we reproduce an effective f(z) and show that this class of models is fairly well compatible with present-time data. To do so, we get numerical constraints employing Monte Carlo fits with the Union 2.1 supernova survey and with the Hubble measurement data set. Keywords: cosmography, f(R) gravity, transition redshift, dark energy | 1237 | ||||