Get6pts {MLDS}

Find All 6-point Conditions in data.frame

Description

Get6pts enumerates all 6-point conditions from a difference scaling experiment and is used as one of the input arguments for calculating an observer's likelihood for his performance on 6-point conditions.

Usage

Get6pts(x, nrep, ...)

Arguments

x

an object of class ‘mlds’.

nrep

integer indicating how many sessions are in the data set.

...

Possibility of sending additional arguments but currently unused.

Details

The 6-point condition is defined on 6-tuples of points, a, b, c, a', b', c', ordered on a physical scale. The condition requires that if the pair (a, b) > (a', b') and the pair (b, c) > (b', c'), then (a, c) > (a', c').

Value

A list of three same size data.frames with an attribute, indices that is a three column data.frame with the same number of rows as each of the three data.frames. Each data.frame is of the format from a difference scaling experiment. Same named rows indicate three trials that form a 6-point condition, i.e., given the 6-tuple of stimuli, a, b, c, a', b', c',

A

data.frame indicating the trials (a, b) vs (a', b')

B

data.frame indicating the trials (b, c) vs (b', c')

E

data.frame indicating the trials (a, c) vs (a', c')

The attribute gives the row numbers from which the trials were obtained from the original data.frame.

Note

It is important that the stimuli are in physical order and not the experimental order. If in experimental order, then SwapOrder should be applied first.

Author(s)

Kenneth Knoblauch

References

Maloney, L. T. and Yang, J. N. (2003) Maximum likelihood difference scaling. Journal of Vision, 3(8):5, 573–585, doi:10.1167/3.8.5.

See Also

SwapOrder, lik6pt, simu.6pt

Examples

data(kk1)
kk.6pt <- Get6pts(mlds(SwapOrder(kk1)), nrep = 1)