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Diffstat (limited to 'probability')
| -rw-r--r-- | probability | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/probability b/probability new file mode 100644 index 0000000..3aa001d --- /dev/null +++ b/probability @@ -0,0 +1,38 @@ +####################################################################### +# Get a result based on a probability (default is 0.5) +# a typical usage is: 'if(pr(x)) then ... +# The default case is equivalent to tossing a coin +# You can pass in a vector of probabilties to get a vector of T, F results +# +pr <- function(x = 0.5){ + if (!length(x)) {return()} + if (x<0 || x>1) stop(" prob out of range\n") + return(ifelse(rbinom(length(x), 1, x), TRUE, FALSE)) +} + + +####################################################################### +# multinomial randomiser; by S.B. extended by S.P. +# n - length of result vector +# p - vector of probabilities; has to sum to <= 1 +# val - vector of return values, with length == p or: +# if longer than p, should be 1 element longer (LAST element is returned) +rMulti <- function(n=1, p, val) { + res <- 1:n + for(i in res) { + element <- ((1:length(p))[runif(1)<cumsum(p)]) + r <-val[element[1]] + if (is.na(r)) r <- val[length(val)] + res[i] <- r + names(res)[i] <- names(r) + } + return(res) +} + +####################################################################### +# calcPert - for Netica - calc Beta params from pert(min, mode, max) +calcPert <- function(mini, mod, maxi) { + alpha <- (4*mod + maxi - 5*mini) / (maxi - mini) + betar <- (5*maxi - mini - 4*mod) / (maxi - mini) + return(unlist(list(alpha=alpha, beta=betar))) +} |