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# scikits.statsmodels.robust.norms.RamsayE.rho

`RamsayE.``rho`(z)

  The robust criterion function for Ramsay’s Ea.

  Parameters: | z : array-like 1d array
  Returns: | array : rho(z) = a**-2 * (1 - exp(-a*|z|)*(1 + a*|z|))

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