Problem in finding starting values for shifted exponential distribution

Question

I am trying to fit shifted exponential distribution to my data but fitdist function giving error of 100 and failing to estimate starting values. I also used plotdist function to find starting or initial values in order to fit the distribution and I have obtained the followings plots with parameters rate = 0.155 shift = 0.00001 after iteration process and even I used these values in fitdist as well. I used mledist function to calculate starting values of distribution parameters as well but it is also not working. I used fitdist function as well it gives the following error:

Error in fitdist(x, "sexp", start = list(rate = 0.155, shift = 1e-05)) : the function mle failed to estimate the parameters, with the error code 100

The code is as below:

library(fitdistrplus)
library(readxl)
library(tidyverse)
library(here)
library(janitor)


# Load data-------------------------------
pvr <- read_excel(here("data", "pvr.xlsx"))

pvr <- pvr %>% 
  select(-starts_with("...")) %>% 
  clean_names(case = "snake")

x <- pvr$headway
rate <- 0.155
shift <- 0.00001
dsexp <- function(x, rate, shift)
  dexp(x-shift, rate=rate)
psexp <- function(x, rate, shift)
  pexp(x-shift, rate=rate)
qsexp <- function(x, rate, shift)
  qexp(x-shift, rate=rate)

f12 <- fitdist(x, "sexp", start = list(rate=0.155, shift=0.00001), lower = c(0, -min(x)))

The data may be downloaded from the following link below:

https://ptagovsa-my.sharepoint.com/:x:/g/personal/kkhan_tga_gov_sa/EfzCE5h0jexCkVw0Ak2S2_MBWf3WUywMd1izw41r0EsLeQ?e=EiqWDc

Can anyone help me in this regard?

Answer 1

The fitdist function uses mle method as default. The code works just by changing the method from mle to mse or mge.