An example of SPEI calculation:

library(SPEI)
library(lmomco)
library(zoo)
library(ggplot2)
library(lubridate)

years <- 1961:1965
months <- 1:12
time <- seq(as.Date("1961/1/1"), as.Date("1965/12/31"), by = "month")
n <- length(time)

# Simulated monthly precipitation (mm), potential evapotranspiration (PET) (mm)
precip <- runif(n, min = 0, max = 200)
pet <- runif(n, min = 50, max = 150)

# Water Balance
wb_ts <- ts(precip - pet, start = c(1961, 1), frequency = 12)

# Calculate SPEI for a 3-month timescale
spei_3 <- spei(wb_ts, scale = 3, na.rm = TRUE)

When I calculate Standardized Precipitation Evapotranspiration Index (SPEI), it has a message below:

“Calculating the Standardized Precipitation Evapotranspiration Index (SPEI) at a time scale of 3. Using kernel type ‘rectangular’, with 0 shift. Fitting the data to a log-Logistic distribution. Using the ub-pwm parameter fitting method. Missing values (NA) will not be considered in the calculation. Using the whole time series as reference period. Input type is vector. No time information provided, assuming a monthly time series.”

It is annoying when I try to calculate a lot of SPEIs using a loop. I already used the suppressMessages funtion below but it did not work:

    fit <- suppressMessages(spei(wb, scale = scale, na.rm = TRUE))
    spei_values <- as.numeric(fit$fitted)