class reliability.Probability_plotting.plotting_positions(failures=None, right_censored=None, a=None, sort=False)

Calculates the plotting positions for plotting on probability paper.

  • failures (array, list) – The failure data. Must have at least 1 element.

  • right_censored (array, list, optional) – The right censored failure data. Optional input. Default = None.

  • a (float, int, optional) – The heuristic constant for plotting positions of the form (k-a)/(n+1-2a) where k is the rank and n is the number of points. Optional input. Default is a = 0.3 which is the median rank method (same as the default in Minitab and Reliasoft). Must be in the range 0 to 1. For more heuristics, see:

  • sort (bool, optional) – Whether the output should be sorted. Default is False.


(array(x),array(y)) (tuple) – a tuple of two arrays. The arrays provide the x and y plotting positions. The x array will match the failures parameter while the y array will be the empirical estimate of the CDF at each of the failures.


This function is primarily used by the probability plotting functions.