R/model-bisse-unresolved.R

In diversitree: Comparative 'Phylogenetic' Analyses of Diversification

## Compute the probabilities of generating every state, given that we
## started with one species in state 0 or state 1.  For lt = length(t)
## times, returns a n(space) x lt x 2 array.
##   'scal': a multiplier to get use of extra precision (the vector
##           will be scaled so that the total probability sums to
##           scal.  Underflow is possible where scal=1, though).
##   'tol': tolerance, used as exit condition (when changes in the
##          probability space do not exceed tol, the step size is good
##          enough).  Lower values _may_ be faster and _may_ have
##          lower accuracy (but with large numbers of clades being
##          calculated, this effect can be small).  It is not clear to
##          me if tol should be resacled by scal before being passed
##          in.
##   'm': parameter affecting internal arguments.  Small numbers often
##        faster, sometimes slower.  Play around.
bucexp <- function(nt, la0, la1, mu0, mu1, q01, q10, t, scal=1,
                   tol=1e-10, m=15) {
  stop("Unresolved clade calculations no longer supported (since 0.10.0)")
}

## This is more useful; given model parameters, and vectors of times
## (t), number of species in each clade (Nc), numbers of species in
## known states (nsc) and numbers of species in state b (k), calculate
## the probabilities of generating the clade, and of extinction.
## Returns a length(t) x 4 matrix, where the first two columns are the
## probabilities of generating the clade, and the second two are the
## probabilities of extinction.
bucexpl <- function(nt, la0, la1, mu0, mu1, q01, q10, t, Nc, nsc, k,
                    scal=1, tol=1e-10, m=15) {
  stop("Unresolved clade calculations no longer supported (since 0.10.0)")
}

## Compute the PDF of the hypergeometric distribution, using the same
## parameters that Wikipedia uses, and I used in the Fortran
## function.
hyperg <- function(N, m, n, k) dhyper(k, m, N-m, n)

## The function 'bucexp.n' creates a data.frame with the number of
## species in state a, b and total for a bucexp state-space absorbing
## at n species.
bucexp.n <- function(n) {
  z <- sapply(0:(n-1), seq, from=0)
  n1 <- unlist(z)
  n0 <- unlist(lapply(z, rev))
  nt <- n0 + n1
  rbind(data.frame(n0, n1, nt), c(NA, NA, n))
}

## Pack a nt x nt matrix with probabilities returned by bucexp().
## Cases where n0 + n1 > nt are given zero probabilities (or change,
## with the 'default' argument; e.g., default=NA will set them to be
## NA).
repack <- function(p, default=0) {
  n <- (sqrt(8*length(p) - 7) - 1)/2
  m <- matrix(default, n, n)
  idx <- bucexp.n(n)
  m[with(idx[-nrow(idx),]+1, cbind(n0, n1))] <- p[-length(p)]
  m
}

## Given two of n0, n1 and nt, calculate the position in the state
## vector.
index <- function(n0, n1, n=n0 + n1) {
  if ( missing(n1) ) n1 <- n - n0
  if ( missing(n0) ) n0 <- n - n1
  stopifnot(n0 + n1 == n && all(n0 >= 0) && all(n1 >= 0))
  n*(n + 1)/2 + 1 + n1
}

## Construct the transition matrix.  Again, non-R style, as this was
## used as a template for constructing the same in Fortran.
make.matrix <- function(nt, lambda0, lambda1, mu0, mu1, q01, q10) {
  ## Diagonals (are linear sums of these: -(n0*r0 + n1*r1)):
  r0 <- lambda0 + mu0 + q01
  r1 <- lambda1 + mu1 + q10

  ## A few useful numbers:
  n1 <- nt*(nt-1)/2
  nm <- n1 + nt + 1

  ## Create some useful vectors
  j1 <- integer(n1)
  n0 <- integer(n1)
  n1 <- integer(n1)
  k <- 1
  for ( i in 1:(nt-1) ) {
    for ( j in 1:i ) {
      j1[k] <- i + k
      n0[k] <- i - j + 1
      n1[k] <- j
      k <- k + 1
    }
  }

  ## Character state transitions and extinctions
  m <- matrix(0, nm, nm)
  for ( i in 1:n1 ) {
    m[j1[i],   i]       <- n0[i]*mu0
    m[j1[i]+1, i]       <- n1[i]*mu1
    m[j1[i],   j1[i]+1] <- n0[i]*q01
    m[j1[i]+1, j1[i]]   <- n1[i]*q10
  }

  ## Speciation and diagonals:
  for ( i in 2:n1 ) {
    if ( n0[i] > 1 )
      m[i, j1[i]]   <- (n0[i]-1)*lambda0
    if ( n1[i] > 1 )
    m[i, j1[i]+1] <- (n1[i]-1)*lambda1
    m[i,i]        <- - (n0[i]-1)*r0 - (n1[i]-1)*r1
  }

  ## Speciation in the special final column, diagonals for the last
  ## class.
  k <- nt*(nt-1)/2
  for ( i in 1:nt ) {
    m[k+i, nm]  <-  (nt-i)*lambda0 + (i-1)*lambda1
    m[k+i, k+i] <- -(nt-i)*r0      - (i-1)*r1
  }

  m
}