makeGlobalStat: Compute global statistic of a variable
Description
Calculates a global summary for CMIP5 data, usually weighted by the
grid cell areas used by each particular model. If no
area weighting is supplied, one is computed based on the lon/lat
values of x. The default statistic is weighted.mean,
but any summary function that returns a numeric result can be used.
Usage
makeGlobalStat(x, area = NULL, verbose = FALSE, FUN = weighted.mean, ...)
Arguments
verbose
logical. Print info as we go?
FUN
function. Function to apply across grid
...
Other arguments passed on to FUN
Value
A cmip5data object, in which the val dimensions are the
same as the caller for Z (if present) and time, but lon and lat are reduced to
1 (i.e. no dimensionality). A numCells field is also added, recording the number
of cells in the spatial grid.
Details
The stat function is calculated for all combinations of lon,
lat, and Z (if present).
This function is more complicated than the other makeXxxStat functions, because
it provides explicit support for area-weighted functions. We expect that
weighted.mean and a weighted sum will be the most frequent
calculations needed. The former is built into R, and the latter can generally
be calculated as weighted.mean * sum(area). A user-supplied stat function must
follow the weighted.mean syntax, in particular
accepting parameters 'x' (data) and 'w' (weights) of equal size, as well as dots(...).
Examples
Run this coded <- cmip5data(1970:1975) # sample data
makeGlobalStat(d)
summary(makeGlobalStat(d))
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