SHELF (version 1.0.1)

SHELF-package: Tools to Support the Sheffield Elicitation Framework

Description

Implements various methods for eliciting a probability distribution for a single parameter from an expert or a group of experts. The expert provides a small number of probability or quantile judgements, corresponding to points on his or her cumulative distribution function. A range of parametric distributions can then be fitted and displayed, with feedback provided in the form of additional quantiles. A graphical interface for the roulette elicitation method is also provided. For multiple experts, a weighted linear pool can be calculated.

Details

ll{ Package: SHELF Type: Package Version: 1.0.1 Date: 2015-07-07 License: GPL-2 | GPL-3 }

References

http://www.tonyohagan.co.uk/shelf/{the SHELF homepage}

See Also

elicit, feedback, fitdist, plinearpool, plotfit, qlinearpool, roulette

Examples

## 1) Elicit judgements from two experts individually 
# Expert 1 states P(X<30)=0.25, P(X<40)=0.5, P(X<50)=0.75
# Expert 2 states P(X<20)=0.25, P(X<25)=0.5, P(X<35)=0.75
# Both experts state 0<X<100.

## 2) Fit distributions to each expert's judgements
v <- matrix(c(30, 40, 50, 20, 25, 35), 3, 2)
p <- c(0.25, 0.5, 0.75)
myfit <- fitdist(vals = v, probs = p, lower = 0, upper = 100)

## 3) Plot the fitted distributions, including a linear pool
plotfit(myfit, lp=T)

## 4) Now elicit a single 'consensus' distribution from the two experts
# Suppose they agree P(X<25)=0.25, P(X<30)=0.5, P(X<40)=0.75
v <-c(25, 30, 40)
p <-c(0.25, 0.5, 0.75)
myfit <- fitdist(vals = v, probs = p, lower = 0, upper = 100)

## 5) Plot the fitted density, and report some feedback, such as the 
# fitted 5th and 95th percentiles
plotfit(myfit, ql=0.05, qu=0.95)
feedback(myfit, quantiles=c(0.05,0.95))

## Can also use interactive plotting
v <- matrix(c(30, 40, 50, 20, 25, 35), 3, 2)
p <- c(0.25, 0.5, 0.75)
myfit <- fitdist(vals = v, probs = p, lower = 0, upper = 100)
# plot each distribution
plotfit(myfit, int = TRUE)

## plot the distribution for one expert only
plotfit(myfit, int= TRUE, ex=1)

## Enter judgements in interactive mode
elicit()

## Enter judgements using the roulette method
roulette(Lo=0, Up=100, nbins=10, gridheight=10)