spi_doc: SPI

In Climandes/ClimIndVis: Calculation, verification and visualisation of climate indices

Description

SPI

Arguments

timescale	Integer. Timescale for monthly SPI calculation. The timescale is the window length (in month) of a backward looking running mean. Default = 6.
ref	Vector with start and end year for reference period. If no reference period is specified, the full period is used as reference period.
distribution	A character string naming a distribution of package stats (see for example GammaDist). For more information on the choice of the distribution, see section Details. Default = "gamma".
limit	Truncate SPI values that are larger than a given threshold, as values larger than 4 are not reasonable. Default = 4. The truncation can be disabled by setting limit = Inf.

Details

The SPI calculation is based on the SCI package from Lukas Gudmundsson & James Stagge. For the SPI calculation, aggt needs to be set to "monthly". For the argument distribution, provide a distribution for which the corresponding density function (dname), the corresponding distribution function (pname) and the quantile function (qname) must be defined (see for example GammaDist). Distributions are listed in the package stats.
Note, that it is important, what distribution you choose for the transformation of your rainfall data. If you are not sure, consider the below references.

References

Stagee, J.H. ; Tallaksen, L.M.; Gudmundsson, L.; van Loon, A.; Stahl, K.: Candidate Distributions for Climatological Drought Indices (SPI and SPEI), 2015, International Journal of Climatology, 35, 4027-4040, doi:10.1002/joc.4267.

Climandes/ClimIndVis documentation built on Oct. 24, 2021, 10:52 a.m.