cal_spei

cal_spei

cal_spei(x, x_ref = x, distribution = "log-Logistic", fit = "ub-pwm", ...)

cal_spi(x, x_ref = x, distribution = "Gamma", fit = "ub-pwm", ...)

Arguments

x

A monthly time series of certain month, which you want to calculate drought index.

x_ref

the reference time series to fit distribution

distribution

Distribution name, one of Normal, Gamma, PearsonIII, log-Logistic.

fit

Fitting method, one of ub-pwm, pp-pwm, max-lik.

...

ignored

Examples

cal_spei(wb)
#> $z
#>  [1]  1.3465967 -0.7975582  1.2282438  1.2105785 -0.8330054 -0.7151369
#>  [7] -1.5750352  0.9450827 -0.2714889 -0.1292077  1.0352074 -0.1584032
#> [13] -0.3685087  0.6378813 -1.1502497 -0.4042817 -1.0129986 -0.5419764
#> [19]  0.4775998  0.8923626  0.3365170  1.0252081  0.5088347 -0.9919120
#> [25]  1.3625166  2.1692985 -1.9216736  0.7380880 -0.5575374 -1.0599387
#> [31] -0.4292552 -0.5776644
#> 
#> $coef
#>         xi      alpha          k 
#> 17.1677346  9.9856074 -0.1882908 
#> 
cal_spei(wb, fit = "max-lik")
#> $z
#>  [1]  1.25999914 -0.77999922  1.15937837  1.14430496 -0.82021583 -0.68766545
#>  [7] -1.74892410  0.91577051 -0.21637171 -0.07341018  0.99379870 -0.10245301
#> [13] -0.31599506  0.64547906 -1.19497621 -0.35318841 -1.02940914 -0.49877715
#> [19]  0.50120971  0.86988475  0.37196947  0.98516596  0.52952607 -1.00445344
#> [25]  1.27348772  1.94605980 -2.27125937  0.73446363 -0.51548045 -1.08541187
#> [31] -0.37930459 -0.53716247
#> 
#> $coef
#>         xi      alpha          k 
#> 16.3022516 10.0289876 -0.2891207 
#> 
cal_spei(wb, distribution = "Normal")
#> $z
#>  [1]  1.3799430 -0.7889772  1.1935245  1.1668933 -0.8144692 -0.7292493
#>  [7] -1.3273864  0.7993825 -0.3936960 -0.2793525  0.9176888 -0.3031498
#> [13] -0.4695109  0.4371980 -1.0381714 -0.4970740 -0.9422990 -0.6014194
#> [19]  0.2690270  0.7329335  0.1304656  0.9042561  0.3008454 -0.9274531
#> [25]  1.4061349  3.2121707 -1.5547703  0.5490491 -0.6130510 -0.9752326
#> [31] -0.5161996 -0.6280507
#> 
#> $coef
#>       mu    sigma 
#> 20.39163 18.77496 
#> 
cal_spi(wb)
#> $z
#>  [1]  1.26240681 -0.76168884  1.15342939  1.13742524 -0.81366784 -0.64809040
#>  [7]        -Inf  0.90368760 -0.14970205 -0.01416018  0.98174660 -0.04135958
#> [13] -0.24717915  0.64416040 -1.40015371 -0.28438051 -1.11586696 -0.43532124
#> [19]  0.51062651  0.85852396  0.39270214  0.97302787  0.53664402 -1.07654690
#> [25]  1.27731342  2.13867280        -Inf  0.72801153 -0.45327061 -1.20776216
#> [31] -0.31080215 -0.47679268
#> 
#> $coef
#>    alpha     beta    pzero 
#>  1.27298 17.43576  0.06250 
#>