UKFE (version 0.4.0)

AnnualStat: Annual statistics extraction

Description

Extracts annual statistics (default maximums) from a data.frame which has dates (or POSIXct) in the first column and variable in the second.

Usage

AnnualStat(
  x,
  Stat = max,
  Truncate = TRUE,
  Mon = 10,
  Hr = 9,
  Sliding = FALSE,
  N = 24,
  ...
)

Value

a data.frame with columns; DateTime and Result. By default Result is the annual maximum sample, but will be any statistic used as the Stat argument.

Arguments

x

a data.frame with dates (or POSIXct) in the first column and variable in the second

Stat

A user chosen function to extract statistics, for example mean. The default it max. User supplied functions could also be used.

Truncate

Logical argument with a default of TRUE. If TRUE, then x is truncated to be within the first and last occurrence of the chosen month and time. If FALSE tuncation is not done and results from partial years will be included.

Mon

Choice of month as a numeric, from 1 to 12. The default is 10 which means the year starts October 1st.

Hr

Choice of hour to start the year (numeric from 0 to 23). The default is 9.

Sliding

Logical argument with a default of FALSE. This can be applied if you want the statistic over a sliding period. For example, deriving maximum annual rainfall totals over a 24 hour period, rather than the maximum daily totals. The number of periods (timesteps) is chosen with the N argument. If for example you want the annual maximum sum of rainfall over a 24 hour period, and you have 15minute data, the Stat input would be sum, and N would be 96 (because there are 96 15 minute periods in 24 hours).

N

Number of timesteps to slide over - used in conjunction with Sliding. The default is 24, make sure to adjust this depending on the duration of interest and the sampling rate of the input data.

...

further arguments for the stat function. Such as na.rm = TRUE.

Author

Anthony Hammond

Details

The statistics are extracted based on the UK hydrological year by default (start month = 10). Month can be changed using the Mon argument. A year is from Mon-Hr to Mon-(Hr-1). For example, the 2018 hydrological year with Hr = 9 would be from 2018-10-01 09:00:00 to 2019-10-01 08:00:00. If Hr = 0, then it would be from 2018-10-01 00:00:00 to 2019-09-30 23:00:00. Data before the first occurrence of the 'start month' and after and including the last occurrence of the 'start month' is not included in the calculation of the statistic.

Examples

#Extract the Thames AMAX daily mean flow and display the first six rows
ThamesAM <- AnnualStat(ThamesPQ[,c(1,3)])
head(ThamesAM)
#Extract the annual rainfall totals.
ThamesAnnualP <- AnnualStat(ThamesPQ[,1:2], Stat = sum)
#Extract maximum five day rainfall totals from the Thames rain
ThamesP5DayAM <- AnnualStat(ThamesPQ[,1:2], Stat = sum, Sliding = TRUE, N = 5)