fasstr: add_rolling_means – R documentation

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add_rolling_means

Add rolling n-day average column(s) to daily flows

Description

Adds selected n-day rolling means to a daily streamflow data set. Based on selected n-days and alignment, the rolling mean for a given day is obtained by averaging the adjacent dates of daily mean values. For example, rolling days of '7' and 'right' alignment would obtain a mean of the given and previous 6 days of daily mean flow.

Usage

add_rolling_means(
  data,
  dates = Date,
  values = Value,
  groups = STATION_NUMBER,
  station_number,
  roll_days = c(3, 7, 30),
  roll_align = "right"
)

Arguments

`data`	Data frame of daily data that contains columns of dates, flow values, and (optional) groups (e.g. station numbers). Leave blank if using `station_number` argument.
`dates`	Name of column in `data` that contains dates formatted YYYY-MM-DD. Only required if dates column name is not 'Date' (default). Leave blank if using `station_number` argument.
`values`	Name of column in `data` that contains numeric flow values, in units of cubic metres per second. Only required if values column name is not 'Value' (default). Leave blank if using `station_number` argument.
`groups`	Name of column in `data` that contains unique identifiers for different data sets, if applicable. Only required if groups column name is not 'STATION_NUMBER'. Function will automatically group by a column named 'STATION_NUMBER' if present. Remove the 'STATION_NUMBER' column beforehand to remove this grouping. Leave blank if using `station_number` argument.
`station_number`	Character string vector of seven digit Water Survey of Canada station numbers (e.g. `"08NM116"`) of which to extract daily streamflow data from a HYDAT database. Requires `tidyhydat` package and a HYDAT database. Leave blank if using `data` argument.
`roll_days`	Numeric values of the number of days to apply a rolling mean. Default `c(3,7,30)`.
`roll_align`	Character string identifying the direction of the rolling mean from the specified date, either by the first (`'left'`), last (`'right'`), or middle (`'center'`) day of the rolling n-day group of observations. Default `'right'`.

Value

A data frame of the source data with an additional column(s):

QnDay

rolling means of the n-day flow values of the designated date and adjacent dates, direction of mean specified by roll_align

Default additional columns:

`Q3Day`	rolling means of the 3-day flow values of the designated date and previous 2 days (roll_align = "right")
`Q7Day`	rolling means of the 7-day flow values of the designated date and previous 6 days (roll_align = "right")
`Q30Day`	rolling means of the 30-day flow values of the designated date and previous 29 days (roll_align = "right")

Examples

# Run if HYDAT database has been downloaded (using tidyhydat::download_hydat())
if (file.exists(tidyhydat::hy_downloaded_db())) {

# Add default 3, 7, and 30-day rolling mean columns, with "right" alignment
add_rolling_means(station_number = "08NM116")

# Add custom 5 and 10-day rolling mean columns
add_rolling_means(station_number = "08NM116",
                  roll_days = c(5,10))
                  
# Add default 3, 7, and 30-day rolling mean columns, with "left" alignment
add_rolling_means(station_number = "08NM116",
                  roll_align = "left")                
                  
}

fasstr

Analyze, Summarize, and Visualize Daily Streamflow Data

v0.3.2

Apache License 2.0

Authors

Jon Goetz [aut, cre] (<https://orcid.org/0000-0002-4993-1119>), Carl James Schwarz [aut], Robin Pike [ctb], Province of British Columbia [cph]

Initial release