getSSTsd:
In galuardi/hmmwoa: bones of a hidden markov model for psat data

1	getSSTsd(psat, surf = -11)

`psat`
`surf`

##---- Should be DIRECTLY executable !! ----
##-- ==>  Define data, use random,
##--	or do  help(data=index)  for the standard data sets.

## The function is currently defined as
function (psat, surf = -11) 
{
    tzidx = psat$Z >= (surf)
    tzidx[is.na(tzidx)] = F
    temp = psat$T
    temp[tzidx == F] = NA
    tsd = apply(temp, 1, sd, na.rm = T)
    tsd[tsd == 0] = NA
    tsd
  }