two.level.comparison.items: Creates a 'compitem' object

Description Usage Arguments Details Value Note Author(s) References See Also Examples

View source: R/two.level.comparison.items.r

Description

This function creates a compitem object from a dataframe or matrix of observations from an item to be deemed a control, or a recovered, item.

Usage

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two.level.comparison.items(dat, data.columns)

Arguments

dat

a matrix or dataframe of observed properties from either the control, or recovered, item

data.columns

a vector of integers giving which columns in dat are the observations of the properties

Details

Takes observations from the control, or recovered, item and makes them into and object which can be passed to either: two.level.density.LR, or, two.level.normal.LR, or, two.level.lindley.LR, for likelihood ratio calculation.

Value

Returns a compitem object

Note

This function, and class it generates, exist to make sure that all the necessary bits and pieces are there to put into the likelihood ratio calculation function

Author(s)

David Lucy [email protected] - http://www.maths.lancs.ac.uk/~lucy

References

Aitken, C.G.G. & Lucy, D. (2004) Evaluation of trace evidence in the form of multivariate data. Applied Statistics: 53(1); 109-122.

See Also

compcovar
compitem
two.level.comparison.items
two.level.components
two.level.density.LR
two.level.normal.LR
two.level.lindley.LR

Examples

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# load this library
library(comparison)

# load Greg Zadora's glass data
data(glass)

# make it into a data frame
dat <- as.data.frame(glass)

# calculate a compcovar object based upon dat
# using K, Ca and Fe - warning - could take time
# on slower machines
Z <- two.level.components(dat, c(7,8,9), 1)

# calculate a compitem object representing the control item
control <- two.level.comparison.items(dat[37:42,], c(7,8,9))

# calculate a compitem object representing the recovered item
# known to be from the same item (item 4)
recovered.1 <- two.level.comparison.items(dat[43:48,], c(7,8,9))

# calculate a compitem object representing the recovered item
# known to be from a different item (item 6)
recovered.2 <- two.level.comparison.items(dat[67:72,], c(7,8,9))

comparison documentation built on May 29, 2017, 9:08 a.m.