EF {qualV}

Efficiency Factor as Suggested by Nash and Sutcliffe

Description

The efficiency factor is a dimensionless statistic which directly relates predictions to observed data.

Usage

EF(o, p)

Arguments

o

vector of observed values

p

vector of corresponding predicted values

Details

Two time series are compared. 'EF' is an overall measure of similarity between fitted and observed values. Any model giving a negative value cannot be recommended, whereas values close to one indicate a 'near-perfect' fit.

Value

EF

efficiency factor

References

Nash, J. E. and Sutcliffe, J. V. (1970) River flow forecasting through conceptual models part I - A discussion of principles. Journal of Hydrology, 10, 282-290.

Mayer, D. G. and Butler, D. G. (1993) Statistical Validation. Ecological Modelling, 68, 21-32.

See Also

MAE, MSE, MAPE, GRI

Examples

# a constructed example
x <- seq(0, 2*pi, 0.1)
y <- 5 + sin(x)           # a process
o <- y + rnorm(x, sd=0.2) # observation with random error
p <- y + 0.1              # simulation with systematic bias

plot(x, o); lines(x, p)
EF(o, p)

# observed and measured data with non-matching time intervals
data(phyto)
obsb <- na.omit(obs[match(sim$t, obs$t), ])
simb <- sim[na.omit(match(obs$t, sim$t)), ]
EF(obsb$y, simb$y)