log likelihood and derivatives for exponential distribution

Usage

llikExp(x, rate, full = FALSE)

Arguments

x: variable that is distributed by exponential distribution
rate: vector of rates.
full: Add the data frame showing x, mean, sd as well as the fx and derivatives

Value

data frame with fx for the log pdf value of with dRate

that has the derivatives with respect to the rate parameter the observation time-point

Details

In an rxode2() model, you can use llikExp() but you have to use the x and rate arguments. You can also get the derivative of rate with llikExpDrate().

Author

Matthew L. Fidler

Examples

# \donttest{
llikExp(1, 1:3)
#>          fx      dRate
#> 1 -1.000000  0.0000000
#> 2 -1.306853 -0.5000000
#> 3 -1.901388 -0.6666667

llikExp(1, 1:3, full=TRUE)
#>   x rate        fx      dRate
#> 1 1    1 -1.000000  0.0000000
#> 2 1    2 -1.306853 -0.5000000
#> 3 1    3 -1.901388 -0.6666667

# You can use rxode2 for these too:

et <- et(1:3)
et$x <- 1

model <- function() {
  model({
    fx <- llikExp(x, time)
    dRate <- llikExpDrate(x, time)
  })
}

rxSolve(model, et)
#>  
#>  
#>  
#>  
#> using C compiler: ‘gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0’
#> ── Solved rxode2 object ──
#> ── Parameters ($params): ──
#> # A tibble: 1 × 0
#> ── Initial Conditions ($inits): ──
#> named numeric(0)
#> ── First part of data (object): ──
#> # A tibble: 3 × 4
#>    time    fx  dRate     x
#>   <dbl> <dbl>  <dbl> <dbl>
#> 1     1 -1     0         1
#> 2     2 -1.31 -0.5       1
#> 3     3 -1.90 -0.667     1
# }