ch_ffa_screen_plot: FFA screening plot

In CSHShydRology: Canadian Hydrological Analyses

FFA screening plot

Description

Generates a flood frequency plot with symbols indicating whether an observation is a high or low outlier, and colour symbols indicating month of the year in which the flood occurred.

Usage

ch_ffa_screen_plot(
  df,
  stn = "unspecified",
  mtitle = "",
  n = 12,
  m = 0,
  M = 2,
  offset = 0,
  mcol = c("orange", "gray70", "red")
)

Arguments

df	dataframe with date of event [maxdate] and annual maximum [amax]
stn	stationID
mtitle	title for plot
n	default is 12, number of colours for number of months
m	smallest angle in radians parameter for generating circular colours default = 0
M	largest angle in radians parameter for generating circular colours default = 2 (*pi)
offset	the zero in radians, default is 0.
mcol	array of three colours, default is c("orange", "gray70", "red") use to outline or emphasize low outliers, normal, and high outliers.

Value

a list containing

• Station if specified else "unspecified"

• number of amax events

• array of amax magnitudes

• array of outlier codes (1 = low, 2 = not, 3 = high outlier)

References

Cohn, T. A., J. F. England, C. E. Berenbrock, R. R. Mason, J. R. Stedinger and J. R. Lamontagne (2013). "A generalized Grubbs‐Beck test statistic for detecting multiple potentially influential low outliers in flood series." Water Resources Research 49(8): 5047-5058 10.1002/wrcr.20392: 10.1002/wrcr.20392.

Examples

# Not tested automatically as can be very slow to execute
data(CAN05AA008)
amax <- ch_sh_get_amax(CAN05AA008)
ch_ffa_screen_plot(amax)

CSHShydRology documentation built on Feb. 4, 2026, 5:06 p.m.