willmott {growR} | R Documentation |
Willmott Index
Description
Willmott's index of model performance as described in Willmott (2012).
Usage
willmott(predicted, observed, ...)
Arguments
predicted |
Vector containing the predictions y. |
observed |
Vector containing the observations z. |
... |
Scaling factor c in the denominator in the Willmott index. The originally proposed value of 2 should be fine. |
Details
This index takes on values from -1 to 1, where values closer to 1 are generally indicating better model performance. Values close to -1 can either mean that the model predictions differ strongly from the observation, or that the observations show small variance (or both).
Value
willmott Value between -1 and 1
References
Willmott CJ, Robeson SM, Matsuura K (2012). “A Refined Index of Model Performance.” International Journal of Climatology, 32(13), 2088–2094. ISSN 1097-0088, doi:10.1002/joc.2419, https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/joc.2419.
See Also
Examples
predicted = c(21.5, 22.2, 19.1)
observed = c(20, 20, 20)
# The Willmott index "fails" in this case, as the variance in the
# observation is 0.
willmott(predicted, observed)
# Try with more realistic observations
observed = c(20.5, 19.5, 20.0)
willmott(predicted, observed)