visualFields (version 0.2-4)

locperc: percentiles for each location

Description

gets the percentiles for each location

Usage

locperc( vals, stds, percentiles = c( 0.5, 1, 2, 5, 95 ),
         type = c( "quantile", "(i-1)/(n-1)", "i/(n+1)", "i/n" ),
         poolLocations = FALSE )

Arguments

vals

table with sensitivity values, total-deviation values, or pattern-deviation values

stds

standard deviations per location for sensitivity values, total-deviation values, or pattern-deviation values

percentiles

percentiles at which to calculate cutoff values

type

see wtd.quantile for a list of different options

poolLocations

assume that the shape of the empirical distributions at each location is the same and pool sensitivity, TD, or PD values per location. This is useful when the number of controls available is small. Sample size is increased at the expense of posible bias d

Value

• percentiles for each location

Details

gets the percentiles at each location. Since the number of visits per subject can be variable. To account for that, weighted quantile is used in which the weights for is the inverse of the number of visits for the subject

All the data passed to the function must belong to the same perimeter tperimetry, the same pattern of locations talgorithm, and the same presentation algorithm tpattern.

References

[1] A. Heijl, G. Lindgren, and J. Olsson. A package for the statistical analysis of visual fields. Documenta Ophthalmologica Proceedings Series, 49, 1987

[2] A. Heijl, G. Lindgren, J. Olsson, and P. Asman. Visual field interpretation with empiric probability maps. Archives of Ophthalmology, 107, 1989

See Also

gloperc

Examples

# DO NOT RUN
# lperc <- locper()