SpatialVx (version 0.1-2)

FeatureSuite: Wrapper function to perform feature-based spatial verification

Description

Wrapper function to perform feature-based spatial verification.

Usage

FeatureSuite(prep.object, fun.object, verbose = FALSE)
FeatureSuitePrep(Fcst.name, Vx.name, loc = NULL, units = NULL)
FeatureFunPrep(identfun = NULL, identfun.args = NULL, mergefun = NULL, mergefun.args = NULL, matchfun = NULL, matchfun.args = NULL, analysisfun = NULL, analysisfun.args = NULL)

Arguments

prep.object

list object as output from the FeatureSuitePrep function.

fun.object

list object as output from the FeatureFunPrep function.

Fcst.name, Vx.name

character giving the name of the fields in the verification set.

loc

(optional) numeric n*m X 2 matrix giving lon/lat coordinates for the verification set. Currently, this is not used for anything, but may have a use in the future, e.g., for adding a map to plots of neighborhood smoothed fields.

units

(optional) character giving the name of the units of the verification set.

identfun,mergefun,matchfun,analysisfun

character specifying a function for performing feature: (i) identification, (ii) merging, (iii) matching and (iv) analyzing the resulting (possibly merged and/or matched) features. The arguments mergefun and matchfun may be left

identfun.args,mergefun.args,matchfun.args,analysisfun.args

list objects containing relevant optional arguments to identfun, mergefun, matchfun, and analysisfun. these may be left NULL. See Details section for specific arguments that each function must take. S

verbose

logical, should progress information be printed to the screen (including total lapsed time)?

Value

• FeatureSuite returns a list object with numbered components depending on the numbers of thresholds (if any) supplied with output from the analysisfun function as well as additional components:
• prep.obj
  character naming the prep object used.
• fun.object
  character naming the function obect supplied to the fun.object argument.
• FeatureSuitePrep returns a list object with components:
• Fcst.name
  character giving the name of the forecast matrix of the verification set.
• Vx.name
  character giving the name of the observed matrix of the verification set.
• xdim
  numeric vector of length 2 giving the dimensions of the verification set.
• loc
  Same as in Arguments above.
• units
  Same as in Arguments above.
• FeatureFunPrep returns a list object with components:
• identify
  list object with components fun and args.
• merge
  list object with components fun and args.
• match
  list object with components fun and args.
• analysis
  list object with components fun and args.
• In each case, fun is a character naming a function, and args is a list object specifying any additional arguments beyond those required as stated in the Details section above.

Details

Several methods for spatial forecast verification have focused on identifying features within the fields of the verification set, and then analyzing them usually after merging and matching features (Ebert and McBride, 2000; Davis et al., 2006a, 2006b; Micheas et al., 2007; Wernli et al., 2008; Lack et al., 2010). These functions are very generic functions that facilitate feature-based verification. Some functions for performing specific methods are supplied such as, convthresh.

Fcst.name and Vx.name should point to gridded fields that can be coerced to class "im" of package spatstat. The functions must take object (same as prep.object above) as an input argument, as well as the following arguments (even if they are simply ignored within the function). Additonal arguments are allowed, and can be accessed via the identfun.args, mergefun.args, etc. arguments above.

identfun: object (same as prep.object above) is the only required input argument.

mergefun: If supplied, must take x (output from identfun).

matchfun: If supplied, must take x (output from identfun), y (the output from mergefun).

analysisfun: x (output from identfun), y (output from mergefun), matches (output from matchfun).

The values returned by each of the above functions may vary substantially provided they all work together.

References

Davis CA, BG Brown, and RG Bullock, 2006a. Object-based verification of precipitation forecasts, Part I: Methodology and application to mesoscale rain areas. Mon. Wea. Rev., 134, 1772--1784.

Davis CA, BG Brown, and RG Bullock, 2006b. Object-based verification of precipitation forecasts, Part II: Application to convective rain systems. Mon. Wea. Rev., 134, 1785--1795.

Ebert, E. E. and J. L. McBride, 2000: Verification of precipitation in weather systems: Determination of systematic errors. J. Hydrology, 239, 179--202.

Lack, S., G.L. Limpert and N.I. Fox, 2010: An object-oriented multiscale verification scheme. Wea. Forecasting, 25, 79--92, DOI: 10.1175/2009WAF2222245.1

Micheas AC, NI Fox, SA Lack, and CK Wikle. 2007. Cell identification and verification of QPF ensembles using shape analysis techniques. J. Hydrology, 343, 105--116.

Wernli, H., M. Paulat, M. Hagen, and C. Frei, 2008: SAL--A novel quality measure for the verification of quantitative precipitation forecasts. Mon. Wea. Rev., 136, 4470--4487.

See Also

connected, tiles, tess, as.im, convthresh

Examples

x <- y <- matrix(0, 10, 12)
x[2:3,c(3:6, 8:10)] <- 1
y[c(4:7, 9:10),c(7:9, 11:12)] <- 1

hold <- FeatureSuitePrep("y", "x")

# Do SAL
holdfun <- FeatureFunPrep(identfun="salIDfun", analysisfun="saller") 
look <- FeatureSuite( hold, holdfun)

data(geom000)
data(geom002)
hold <- FeatureSuitePrep("geom002", "geom000")
holdfun <- FeatureFunPrep(identfun="salIDfun", identfun.args=list(thresh=0.1), analysisfun="saller")

look <- FeatureSuite(hold, holdfun)

## Try to make a good example!!
hold <- FeatureSuitePrep("pert004", "pert000")
holdfun <- FeatureFunPrep(identfun="convthresh", identfun.args=list(smoothpar=5.5, thresh=0.01), analysisfun="FeatureMatchAnalyzer")
look <- FeatureSuite(hold, holdfun)