  1.  NAME

  flag_bad - Flag data as bad in a vector

  2.  SYNOPSIS

  [v, mask] = flag_bad(v, sig_max )

  3.  DESCRIPTION

  Calculate the mean value of the non-NaN in a vector, standard
  deviation and residuals for each element. An element is considered as
  bad if the absolute value of its residual is larger than a certain
  threshold value. The latter is determined as a factor times the
  standard deviation.

  This function can be used to detect vector elements that are much more
  different than the other ones.

  4.  PARAMETERS

     v  Data vector.

     sig_max
        Factor used to calculate the threshold value. A typical value is
        2.5.

  5.  RETURNS

     v  Vector with bad elements replaced by NaN.

     mask
        Vector of ones or zeros,zeros specifying elements in v that have
        been flagged as bad,or that were already set to NaN on input.

  6.  AUTHORS

  Pierre Jaccard, Geophysical Institute, University of Bergen, 1999

