Description Usage Arguments Details Value References See Also Examples

Given a set of predictions and a corresponding set of observations, the geometric validation index is a reliability index for the predictions.

1 | ```
GRI(o, p)
``` |

`o` |
vector of observed values |

`p` |
vector of corresponding predicted values |

One possible interpretation of 'GRI' is that the simulation is accurate within a multiplicative factor 'GRI', i.e. the observed values fall between 1/GRI and GRI times of the corresponding predicted values. Values close to one indicate a good match.

`GRI` |
geometric reliability index |

Leggett, L. R. and Williams, L. R. (1981) A reliability index for models. Ecological Modelling, 13, 303-312.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 | ```
# 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)
GRI(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)), ]
GRI(obsb$y, simb$y)
``` |

Embedding an R snippet on your website

Add the following code to your website.

For more information on customizing the embed code, read Embedding Snippets.