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logcondens (version 2.0.6)

MLE: Unconstrained piecewise linear MLE

Description

Given a vector of observations ${\bold{x}} = (x_1, \ldots, x_m)$ with pairwise distinct entries and a vector of weights ${\bold{w}}=(w_1, \ldots, w_m)$ s.t. $\sum_{i=1}^m w_i = 1$, this function computes a function $\widehat \phi_{MLE}$ (represented by the vector $(\widehat \phi_{MLE}(x_i))_{i=1}^m$) supported by $[x_1, x_m]$ such that $$L(\phi) = \sum_{i=1}^m w_i \phi(x_i) - \sum_{j=1}^{m-1} (x_{j+1} - x_j) J(\phi_j, \phi_{j+1})$$ is maximal over all continuous, piecewise linear functions with knots in ${x_1, \ldots, x_m}$

Usage

MLE(x, w = NA, phi_o = NA, prec = 1e-7, print = FALSE)

Arguments

x
Vector of independent and identically distributed numbers, with strictly increasing entries.
w
Optional vector of nonnegative weights corresponding to ${\bold{x}_m}$.
phi_o
Optional starting vector.
prec
Threshold for the directional derivative during the Newton-Raphson procedure.
print
print = TRUE outputs log-likelihood in every loop, print = FALSE does not. Make sure to tell R to output (press CTRL+W).

Value

  • phiResulting column vector $(\widehat \phi_{MLE}(x_i))_{i=1}^m.$
  • LValue $L(\widehat \phi_{MLE})$ of the log-likelihood at $\widehat \phi_{MLE}.$
  • FhatVector of the same length as ${\bold{x}}$ with entries $\widehat F_{MLE,1} = 0$ and $$\widehat F_{MLE,k} = \sum_{j=1}^{k-1} (x_{j+1} - x_j) J(\phi_j, \phi_{j+1})$$ for $k \ge 2.$