d1 function

Modified Index of Agreement (d1).

It estimates the modified index of agreement (d1) using absolute differences following Willmott et al. (1985).

d1(data = NULL, obs, pred, tidy = FALSE, na.rm = TRUE)

Arguments

• data: (Optional) argument to call an existing data frame containing the data.
• obs: Vector with observed values (numeric).
• pred: Vector with predicted values (numeric).
• tidy: Logical operator (TRUE/FALSE) to decide the type of return. TRUE returns a data.frame, FALSE returns a list; Default : FALSE.
• na.rm: Logic argument to remove rows with missing values (NA). Default is na.rm = TRUE.

Returns

an object of class numeric within a list (if tidy = FALSE) or within a data frame (if tidy = TRUE).

Details

Similar to d, the d1 index it is a normalized, dimensionless metric that tests general agreement. The difference with d, is that d1 uses absolute residuals instead of squared residuals. It is bounded between 0 and 1. The disadvantage is that d is an asymmetric index, that is, dependent to the orientation of predicted and observed values. For the formula and more details, see online-documentation

Examples

set.seed(1)
X <- rnorm(n = 100, mean = 0, sd = 10)
Y <- rnorm(n = 100, mean = 0, sd = 9)
d1(obs = X, pred = Y)

References

Willmott et al. (1985). Statistics for the evaluation and comparison of models. J. Geophys. Res. 90, 8995. tools:::Rd_expr_doi("10.1029/jc090ic05p08995")