SPIFromParameters: Calculation of standardized precipitation index from alpha...

In SPIGA: Compute SPI Index using the Methods Genetic Algorithm and Maximum Likelihood

Description

calculate the standardized precipitation index, from alpha and beta parameter of the Gamma function.

Usage

SPIFromParameters(Pmon, scale =3, Param_Alpha, Param_Beta)

Arguments

Pmon	monthly precipitation series ordered according to time. It is a data frame with columns: year, month, station 1, station 2, etc.
scale	an integer value representing the time scale of analysis. The most common are 1, 3, 6, 9, 12, 48, etc.
Param_Alpha	data frame monthly data values corresponding to the alpha parameter to the function Gamma.
Param_Beta	data frame monthly data values corresponding to the alpha parameter to the function Gamma.

Details

Analysis stations are in the columns of dataframe. the apha and beta parameters, are monthly and are in the rows of dataframe.

Input data

similar to Pm_Pisco.

Mon	st_1	st_1	st_2	st_3
Jan	9.584860915	9.227918987	10.35269003	8.433823824
Feb	13.76378505	15.02620223	12.1021093	10.85133914
Mar	26.09112343	17.41749632	21.10924889	23.53649421
Apr	17.34996675	17.4451073	13.00894394	16.66595319
May	9.943259493	9.46815537	9.164645239	9.455850664
Jun	5.103175852	5.041710686	4.080851346	5.790986084
Jul	2.85804336	3.042484994	2.797962575	2.645188236
Aug	3.033862506	3.183267843	3.435303986	2.631287947
Sep	3.815308513	2.627317533	3.550365645	3.66482456
Oct	7.430925356	3.956716609	7.023105167	7.540706878
Nov	6.303310502	5.339943557	6.358902249	5.556660824
Dec	5.84110559	5.899534971	6.581657735	4.889599504

Value

return values of standardized precipitation index in .txt formats.

Author(s)

Iv<c3><a1>n Arturo Ayala Bizarro <[e-mail]>

Jessica Z<c3><ba><c3><b1>iga Mendoza <[e-mail]>

References

McKee, Thomas B. and Doesken, Nolan J. and Kleist, John. 1993. The relationship of Drought Frecuency and Duration to Time Scales. Eighth Conference on Applied Climatology

A. Belauneh and J. Adamowski. Standard Precipitation Index Drought Forecasting Using Neural Networks, Wavelet Neural Networks, and Support Vector Regression. Applied Computational Intelligence and Soft Computing, http://dx.doi.org/10.1155/2012/794061

Examples

#### Load data
data(Pm_Pisco)
data(alphaGA_SPI3)
data(betaGA_SPI3)

#### Computing SPI with Genetic Algorithms
Pmon<-Pm_Pisco
Param_Alpha <- alphaGA_SPI3
Param_Beta <- betaGA_SPI3
SPIFromParameters(Pmon, scale =3, Param_Alpha, Param_Beta)

Example output

Loading required package: GA
Loading required package: foreach
Loading required package: iterators
Package 'GA' version 3.0.1
Type 'citation("GA")' for citing this R package in publications.
********** Calculation Station Pm_St1 
********** Calculation Station Pm_St2 
********** Calculation Station Pm_St3 
********** Calculation Station Pm_St4 

SPIFromParameters: Successful Analysis
See the results:  /work/tmp 

SPIGA documentation built on May 2, 2019, 6:32 a.m.