Description Usage Arguments Value References See Also Examples

Seasonal Kendall permutation test on censored data

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`time` |
Column of the time variable, either a sequence of days or decimal times, etc. Will be the scale used for time in the trend analysis. |

`y` |
The column of y (response variable) values plus detection limits |

`y.cen` |
The y-variable indicators, where 1 (or |

`group` |
Column of the season classifications. A factor in R, so usually though not necessarily a text variable. If numeric, define as a factor before running the script. |

`LOG` |
Indicator of whether to compute the trend analysis in the original y units, or on their logarithms. The default is to use the logarithms (LOG = |

`R` |
The number of repetitions in the permutation process. R is often between 999 and 9999 (adding +1 to represent the observed test statistic produces 1000 to 10000 repetitions). By default R=4999. Increasing R results in lower variation in the p-values produced between runs. |

`nmin` |
The minimum number of observations needed for the entire time period to be tested, per season. For example, with 1 sample per year per season over an 8-year period, you have 8 observations for each season. You can increase this number if you want a higher minimum. Donâ€™t decrease it below the default of 4. If there are fewer than nmin values that season is skipped and not included in the overall test and a note of this will be printed in the console. |

`seaplots` |
In addition to the plot of the overall Seasonal Kendall trend line, plots of the trend in individual seasons can also be drawn. |

`printstat` |
Logical |

Prints the Kendall trend test results for each season individually. The overall Seasonal Kendall test and Theil-Sen line results are both printed and returned.

If `seaplots=TRUE`

each season's trend line will be plotted seperately. A plot of the overall Seasonal Kendall (Akritas-Theil-Sen) line is always plotted.
If `seaplots=FALSE`

only the overall Seasonal Kendall (Akritas-Theil-Sen) line will be plotted on a data scatterplot.

Helsel, D.R., 2011. Statistics for censored environmental data using Minitab and R, 2nd ed. John Wiley & Sons, USA, N.J.

Hirsch, R.M., Slack, J.R., Smith, R.A., 1982. Techniques of Trend Analysis for Monthly Water Quality Data, Water Res. Reseach 18, 107-121.

NADA::cenken

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