pfactor: P-factor

In hydroGOF: Goodness-of-Fit Functions for Comparison of Simulated and Observed Hydrological Time Series

P-factor

Description

P-factor is the percent of observations that are within the given uncertainty bounds.

Ideally, i.e., with a combination of model structure and parameter values that perfectly represents the catchment under study, and in absence of measurement errors and other additional sources of uncertainty, all the simulated values should be in a perfect match with the observations, leading to a P-factor equal to 1, and an R-factor equal to zero. However, in real-world applications we aim at encompassing as much observations as possible within the given uncertainty bounds (P-factor close to 1) while keeping the width of the uncertainty bounds as small as possible (R-factor close to 0), in order to avoid obtaining a good bracketing of observations at expense of uncertainty bounds too wide to be informative for the decision-making process.

Usage

pfactor(x, ...)

## Default S3 method:
pfactor(x, lband, uband, na.rm=TRUE, ...)

## S3 method for class 'data.frame'
pfactor(x, lband, uband, na.rm=TRUE, ...)

## S3 method for class 'matrix'
pfactor(x, lband, uband, na.rm=TRUE, ...)

Arguments

x	ts or zoo object with the observed values.
lband	numeric, ts or zoo object with the values of the lower uncertainty bound
uband	numeric, ts or zoo object with the values of the upper uncertainty bound
na.rm	a logical value indicating whether 'NA' values should be stripped before the computation proceeds.
...	further arguments passed to or from other methods.

Value

Percent of the x observations that are within the given uncertainty bounds given by lband and uband.

If sim and obs are matrixes, the returned value is a vector, with the P-factor between each column of sim and obs.

Note

So far, the argument na.rm is not being taken into account.

Author(s)

Mauricio Zambrano Bigiarini <[e-mail]>

References

Abbaspour, K.C.; Faramarzi, M.; Ghasemi, S.S.; Yang, H. (2009), Assessing the impact of climate change on water resources in Iran, Water Resources Research, 45(10), W10,434, doi:10.1029/2008WR007615.

Abbaspour, K.C., Yang, J. ; Maximov, I.; Siber, R.; Bogner, K.; Mieleitner, J. ; Zobrist, J.; Srinivasan, R. (2007), Modelling hydrology and water quality in the pre-alpine/alpine Thur watershed using SWAT, Journal of Hydrology, 333(2-4), 413-430, doi:10.1016/j.jhydrol.2006.09.014.

Schuol, J.; Abbaspour, K.C.; Srinivasan, R.; Yang, H. (2008b), Estimation of freshwater availability in the West African sub-continent using the SWAT hydrologic model, Journal of Hydrology, 352(1-2), 30, doi:10.1016/j.jhydrol.2007.12.025

Abbaspour, K.C. (2007), User manual for SWAT-CUP, SWAT calibration and uncertainty analysis programs, 93pp, Eawag: Swiss Fed. Inst. of Aquat. Sci. and Technol. Dubendorf, Switzerland.

See Also

rfactor, plotbands

Examples

x <- 1:10
lband <- x - 0.1
uband <- x + 0.1
pfactor(x, lband, uband)

lband <- x - rnorm(10)
uband <- x + rnorm(10)
pfactor(x, lband, uband)

#############
# Loading daily streamflows of the Ega River (Spain), from 1961 to 1970
data(EgaEnEstellaQts)
obs <- EgaEnEstellaQts

# Selecting only the daily values belonging to the year 1961
obs <- window(obs, end=as.Date("1961-12-31"))

# Generating the lower and upper uncertainty bounds, centred at the observations
lband <- obs - 5
uband <- obs + 5

pfactor(obs, lband, uband)

# Randomly generating the lower and upper uncertainty bounds
uband <- obs + rnorm(length(obs))
lband <- obs - rnorm(length(obs))

pfactor(obs, lband, uband)

hydroGOF documentation built on Nov. 4, 2024, 5:08 p.m.