SDI {drought} | R Documentation |
Compute the standardized drought index
Description
Based on the vector of monthly variables, the standardized drought index is computed. Note here the standardized precipitation index (SPI) is used as the example of the drought index in the univariate case. It also represents other drought indices computed in the similar way as SPI.
Usage
SDI(X, ts = 6, dist = "EmpGrin")
Arguments
X |
The vector of a monthly hydro-climatic variable of n years. |
ts |
is the accumulated time scale. |
dist |
is a distribution function.The inputs can be "EmpGrin","EmpWeib","Gamma","Lognormal". |
Details
Apart from the standardized drought index, the percentile (probability) is also provided,
Value
The (univariate) standardized drought index of different time scales from both the empirical and parametric distribution
Examples
X=runif(120, min = 0, max = 100) # 10-year monthly data
fit<-SDI(X,ts=3) # Compute the 3 month drought index
fit$SDI # Get the empirical drought index
z=matrix(t(fit$SDI),ncol=1)
plot(z, type="l", col=1, lwd=2, lty=1, xlim=c(0,120),xlab="Time",ylab="SDI")
[Package drought version 1.2 Index]