grow_seas: Calculate the Start and End of the Growing Season
In treenet/treenetproc: Clean, Process and Visualize Dendrometer Data

Description Usage Arguments Details Value References Examples

grow_seas returns the day of year of growth onset and cessation. Values are returned starting from the second year only, since the calculation depends on the previous year (see Details for further information on the calculation).

1	grow_seas(dendro_L2, tol_seas = 0.05, agg_yearly = TRUE, tz = "UTC")

`dendro_L2`	input `data.frame` containing cleaned `L2` dendrometer data (obtained from functions `proc_dendro_L2` or `corr_dendro_L2`).
`tol_seas`	numeric, defines the amount of yearly growth that needs to be surpassed before `gro_start` is defined. Likewise, `1 - tol_seas` is the amount of yearly growth at which `gro_end` is defined.
`agg_yearly`	logical, specify whether the output is aggregated by year (`agg_yearly = TRUE`) or appended to the `L2` data (`agg_yearly = FALSE`).
`tz`	specify the desired time zone. Default is `"UTC"`.

gro_start is defined as the day of year at which the maximum dendrometer value of the previous year is surpassed. gro_end is defined as the day of year at which the maximum dendrometer value is reached.

To reduce the influence of potential remaining outliers on gro_start and gro_end, an adjustable tolerance tol_seas value is used to define growth start and cessation. That is, by default gro_start represents the day of year at which 5 day of year at which 95 (2020) for a graphical example.

The following variables are returned by grow_seas:

`series`	name of the dendrometer series
`year`	year
`gro_start`	day of year at which growth starts
`gro_end`	day of year at which growth ends

In case data is not aggregated to yearly values (agg_yearly = FALSE), all columns are appended to the output data. The values of gro_start and gro_end are only pasted at the first timestamp of the year, all other rows are set to NA.

Knüsel S., Haeni M., Wilhelm M., Peters R.L., Zweifel R. 2020. treenetproc: towards a standardized processing of stem radius data. In preparation.