A simple supergravity model of inflation constrained with Planck 2018
  data
  We study a model of inflation based on $\mathcal{N}=1$ supergravity
essentially depending on one effective parameter. Under a field transformation
we show that this model turns out to be equivalent to a previously studied
supergravity model known to be ruled out with the original choice of the
parameter. Such parameter measures the slope of the potential at observable
scales. Through a Bayesian parameter estimation, it is shown how this model is
compatible with recent CMB temperature measurements by {\it Planck 2018} giving
rise to a simple, viable, single field model of inflation. The tensor to scalar
ratio constraint is found to be $r_{0.002}<0.065$ with negative running. We
discuss how observables are invariant under the field transformation which
leaves unaltered the slow-roll parameters. As a consequence the use of one
presentation of the model or its field-transformed version is purely a matter
of convenience.
