Time series vector, or time series matrix with column names
plot
Should the results be plotted?
type
Type of trend to be plotted, actual or relative to series median
pval
p-value for significance
...
Further options to pass to plotting function
Details
The Mann-Kendall test is applied for each season and series (in the case of a matrix). The actual and relative Sen slope (actual divided by median for that specific season and series); the p-value for the trend; and the fraction of missing slopes involving the first and last fifths of the data are calculated (see mannKen).
If plot = TRUE, each season for each series is represented by a bar showing the trend. The fill colour indicates whether p < 0.05 or not. If the fraction of missing slopes is 0.5 or more, the corresponding trends are omitted.
Parameters can be passed to the plotting function, in particular, to facet_wrap in ggplot2. The most useful parameters here are ncol (or nrow), which determines the number of columns (or rows) of plots, and scales, which can be set to "free_y" to allow the y-axis to change for each time series. Like all ggplot2 objects, the plot output can also be customized extensively by modifying and adding layers.
Value
A data frame with the following fields:
series
series names
season
season number
sen.slope
Sen slope in original units per year
sen.slope.rel
Sen slope divided by median for that specific season and series
p
p-value for the trend according to the Mann-Kendall test.
missing
Proportion of slopes joining first and last fifths of the data that are missing