spec_spei: spec_spei

In seschaub/getSpei: getSpei converting SPEI netCDF files to R data frames. R package.

Description

spec_spei converts SPEI netCDF files of the Global SPEI database into a data frame and matches automatically locations with SPEI data. This function allows to set a specific start and end year and to specify locations. Note that this function is based on SPEI data, which starts in 1901 (current standard). The SPEI is only available for land and not for water area (see here).

Usage

spec_spei(spei_files, start_y, end_y, locations)

Arguments

spei_files	spei_files is a vector of strings. The strings are the SPEI netCDF filenames without filename extensions (i.e. .nc). netCDF files need to be downloaded from the Global SPEI database before using this function.
start_y	start_y indicates the first year requested of the SPEI data.
end_y	end_y indicates the last year requested of the SPEI data.
locations	locations is a data frame consisting out of three variables: location, longitude and latitude. Note that SPEI values are provided for every x.25 and x.75 coordinates, therefore, spec_spei automatically searches for the closest location on land available. Still coordinates need to refer to a land location.

Note

The function returns location_id: location id, provided by user. longitude_loc: longitude of location, provided by user. latitude_loc: latitude of location, provided by user. lon: longitude from which SPEI value is taken. lat: latitude from which SPEI value is taken. year: respective year month: respective month speixx: respective SPEI

Some initial ideas for the function are based on a work from Bartlein P. J. (R for Earth-System Science).

SPEI values should be compared with values available in the SPEI Global Drought Monitor

Author(s)

Sergei Schaub, ETH Zürich, Agricultural Economics and Policy Group & Grassland Sciences Group

Please cite the package as: Schaub, S. (2019) getSpei: converting SPEI netCDF files to R data frames. R package. Version 3.4.19

References

Beguería, S., Latorre, B., Reig, F. & Vicente-Serrano, S.M. (2019) The Standardised Precipitation-Evapotranspiration Index (http://spei.csic.es/index.html)

See Also

all_spei, all_spei_viz

Examples

# set working directory to directory where speixx.nc files are stored. 
workdir <- "H:/folder1/folder2"
setwd(workdir)

# create data frame of three Vienna, Zurich, New York City
location_id  <- c("Vienna", "Zurich", "New York City")
longitude    <- c(16.37,8.54,-74.25)
latitude     <- c(48.20,47.37,40.71)
locations_df <- data.frame(location_id, longitude, latitude)

# run function
d1 <- spec_spei(spei_files = c("spei01","spei06","spei12"), start_y = 2003, end_y = 2004, locations = locations_df)

For a complete demonstration of this package, refer to getSpei website

seschaub/getSpei documentation built on May 5, 2019, 8:16 a.m.