Glass Transfer, Persistence and Recovery Probabilities

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Description

Simulate the number of glass fragments recovered given the conditions set by the user.

Usage

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transfer(N = 10000, d = 0.5, deffect = 1, lambda = 120, Q = 0.05, l0 =
0.8, u0 = 0.9, lstar0 = 0.1, ustar0 = 0.15, lj = 0.45, uj = 0.7, lstarj
= 0.05, ustarj = 0.1, lR = 0.5, uR = 0.7, t = 1.5, r = 0.5)

Arguments

N

Simulation size

d

The breaker's distance from the window

deffect

Distance effect. deffect = 1 when distance effect exists. Otherwise deffect = 0.

lambda

The average number of glass fragments transferred to the breaker's clothing.

Q

Proportion of high persistence fragments.

l0

Lower bound on the percentage of fragments lost in the first hour

u0

Upper bound on the percentage of fragments lost in the first hour

lstar0

Lower bound on the percentage of high persistence fragments lost in the first hour

ustar0

Upper bound on the percentage of high persistence fragments lost in the first hour

lj

Lower bound on the percentage of fragments lost in the j'th hour

uj

Upper bound on the percentage of fragments lost in the j'th hour

lstarj

Lower bound on the percentage of high persistence fragments lost in the j'th hour

ustarj

Upper bound on the percentage of high persistence fragments lost in the j'th hour

lR

Lower bound on the percentage of fragments expected to be detected in the lab

uR

Upper bound on the percentage of fragments expected to be detected in the lab

t

Time between commission of crime and apprehension of suspect

r

Probability r in ti ~ NegBinom(t, r)

Value

Y

The simulated values of recovered glass fragments

para

Input parameters

Author(s)

James Curran and TingYu Huang

References

Curran, J. M., Hicks, T. N. & Buckleton, J. S. (2000). Forensic interpretation of glass evidence. Boca Raton, FL: CRC Press.

Curran, J. M., Triggs, C. M., Buckleton, J. S., Walsh, K. A. J. & Hicks T. N. (January, 1998). Assessing transfer probabilities in a Bayesian interpretation of forensic glass evidence. Science & Justice, 38(1), 15-21.

Examples

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library(tfer)

## create a transfer object using default arguments
y = transfer()

## probability table
probs = tprob(y)

## extract the probabilities of recovering 8 to 15
## glass fragments given the user-specified arguments
tprob(y, 8:15) 

## produce a summary table for a transfer object
summary(y)

## barplot of probabilities (default)
plot(y, ptype = 0)
plot(y)

## barplot of transfer frequencies
plot(y, ptype = 1)

## histogram
plot(y, ptype = 2)