Plot monthly means and add long-term mean annual discharge percentages. Calculates statistics
from all values, unless specified. Mean data calculated using `calc_longterm_daily_stats()`

function.
Returns a list of plots.

```
plot_monthly_means(
data,
dates = Date,
values = Value,
groups = STATION_NUMBER,
station_number,
roll_days = 1,
roll_align = "right",
water_year_start = 1,
start_year,
end_year,
exclude_years,
months = 1:12,
plot_months = 1:12,
complete_years = FALSE,
ignore_missing = FALSE,
include_title = FALSE,
percent_MAD = c(10, 20, 100)
)
```

- data
Data frame of daily data that contains columns of dates, flow values, and (optional) groups (e.g. station numbers). Leave blank or set to

`NULL`

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 or set to`NULL`

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 value of the number of days to apply a rolling mean. Default

`1`

.- 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'`

.- water_year_start
Numeric value indicating the month (

`1`

through`12`

) of the start of water year for analysis. Default`1`

.- start_year
Numeric value of the first year to consider for analysis. Leave blank or set well before start date (i.e.

`1800`

) to use from the first year of the source data.- end_year
Numeric value of the last year to consider for analysis. Leave blank or set well after end date (i.e.

`2100`

) to use up to the last year of the source data.- exclude_years
Numeric vector of years to exclude from analysis. Leave blank or set to

`NULL`

to include all years.- months
Numeric vector of months to include in analysis. For example,

`3`

for March,`6:8`

for Jun-Aug or`c(10:12,1)`

for first four months (Oct-Jan) when`water_year_start = 10`

(Oct). Default summarizes all months (`1:12`

).- plot_months
Numeric vector of months to include on the plot after calculating statistics. For example,

`3`

for March or`6:8`

for Jun-Aug. Differs from 'months' argument where that argument filters for specific months, this one just chooses which months to plot. Default`1:12`

.- complete_years
Logical values indicating whether to include only years with complete data in analysis. Default

`FALSE`

.- ignore_missing
Logical value indicating whether dates with missing values should be included in the calculation. If

`TRUE`

then a statistic will be calculated regardless of missing dates. If`FALSE`

then only those statistics from time periods with no missing dates will be returned. Default`FALSE`

.- include_title
Logical value to indicate adding the group/station number to the plot, if provided. Default

`FALSE`

.- percent_MAD
Numeric vector of percentages of long-term mean annual discharge to add to the plot (ex.

`20`

for 20 percent MAD or`c(5,10,20)`

for multiple percentages). Set to`NA`

for none. Default`c(10,20,100)`

.

A list of ggplot2 objects for with the following plots for each station provided:

- Annual_Means
a plot that contains annual means with the long-term mean as the x-axis intercept

```
# Run if HYDAT database has been downloaded (using tidyhydat::download_hydat())
if (file.exists(tidyhydat::hy_downloaded_db())) {
# Plot monthly means
plot_monthly_means(station_number = "08NM116",
complete_years = TRUE)
# Plot mean flows with custom LTMADs
plot_monthly_means(station_number = "08NM116",
complete_years = TRUE,
percent_MAD = c(5,10,20,100))
# Plot mean flows and plot just summer months
plot_monthly_means(station_number = "08NM116",
complete_years = TRUE,
plot_months = 6:9)
}
#> $Monthly_Means
#> Warning: Removed 8 rows containing missing values (`position_stack()`).
#>
```