This function classifies time series as "useful", "doubtful" or "suspect", based on 4 homogeneity tests (see below). It follows the Algorithm Theoretical Basis Document (ATBD) of the European Climate Assessment & Dataset project (ECA&D), hosted by the Dutch meteorological service KNMI.

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`X` |
A |

If X is an object of `dataclim`

, the function calls
the 4 homogeneity tests Standard Normal
Homogeneity test (SNHtest), the BuisHand Range test (BHRtest), the PETtitt
test (PETtest) and the VON Neumann ratio (VONtest) and, for temperature,
applies them to annual means of daily temperature ranges (Tmax-Tmin)
and the day-to-day difference of the daily temperature ranges. For
precipitation, the annual counts of days with more than 1mm of rain
are evaluated.

If no more than one test indicates a break at the 1% level of significance, the temperature or precipitation observations are considered as "useful". If two tests indicate a break at the 1% level, the respective observations are considered as "doubtful". With three or more tests indicating breaks at the 1% level, the respective observations are considered as "suspect". The two derived temperature characteristics are aggregated by using the maximum number of 1%-significant breaks.

Note that the four tests cannot handle NAs. If X is a
`dataclim`

object and the derived annual means have missing values, the function
checks whether there are at least 20 valid years and at least 70% of
the years are valid for all variables. In this case, the missing
values are linearly interpolated.

If X is a `data.frame`

, the function assumes the data.frame to
contain equidistant non-NA observations. The series are tested
directly, without any processing of derived quantities as in the case
of the `dataclim`

object.

A list of

`tests ` |
A data.frame with the significance levels (Not Significant, NS - 5% significance level, p5 - 1% significance level, p1) for each test for the (derived annual) variables. |

`breaks ` |
A data.frame with the approximate locations of the break
for each test for the (derived annual) variables (except for the
VONtest). For the |

`classes ` |
A named vector containing the resulting classification of temperature and precipitation as "useful", "doubtful" or "suspect". |

Boris Orlowsky <boris@climate-babel.org>

The ATBD: http://www.ecad.eu/documents/atbd.pdf

`SNHtest`

, `BHRtest`

,
`PETtest`

, `VONtest`

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