HH (version 3.1-32)

OddsRatio: Calculate or plot the odds ratio for a 2x2 table of counts.

Description

Calculate or plot the odds ratio for a 2x2 table of counts. The plot shows the confidence intervals on the probability of row2 for fixed odds ratio and specified probability for row1.

Usage

OddsRatio(x, alpha = 0.05)
plotOddsRatio(x, ylab="prob(col1 | row1)", xlab="prob(col1 | row2)", alpha=c(.50, .05), col=trellis.par.get("superpose.line")$col, lwd=trellis.par.get("superpose.line")$lwd, lwd.reference=1, ...)
plotOddsRatio.base(x, ylab = "prob(col1 | row1)", xlab = "prob(col1 | row2)", alpha = c(0.05, 0.5), legend.x=1.05, oma=c(0,0,0,5), ...)

Arguments

x

2 x 2 table of counts

alpha

Significance levels of test. OddsRatio requires a single number in the range [0,1]. plotOddsRatio accepts more than one number on the range [0,1] and draws confidence lines at each value.

xlab, ylab

x- and y-labels for the plot Sensible defaults are generated.

col, lwd

Colors and linewidths to be used in the graph.

lwd.reference

linewidth for reference line.

...

other arguments, currently ignored.

legend.x

x position of left-hand side of legend.

oma

outer margin par()$oma, needed to make room for legend.

Value

plotOddsRatio returns a lattice object.The older plotOddsRatio.base draws a plot with base graphics and invisibly returns the same list as OddsRatio returns for the first value of alpha.OddsRatio returns the list:

p1, p2

proportion of each row total observed in the first column.

omega1, omega2

odds for each row, p/(1-p)

psihat

odds ratio, omega2/omega1

s.ln.psihat

standard deviation of ln(psihat)

ci.ln.psihat

confidence interval for ln(psihat) using normal approximation

ci.psihat

confidence interval for psihat calculated ase p(ci.ln.psihat)

prob1

seq(0,1,.05), set of p1 values for plotting.

odds1

p1/(1-p1)

odds2

odds for the second row needed to retain psihat with the specified odds1, calculated as odds1*psihat.

ci.odds2

confidence interval for odds2

prob2

odds2 / (odds2+1)

ci.prob2

ci.odds2 / (ci.odds2+1)

References

Heiberger, Richard M. and Holland, Burt (2004b). Statistical Analysis and Data Display: An Intermediate Course with Examples in S-Plus, R, and SAS. Springer Texts in Statistics. Springer. ISBN 0-387-40270-5.

Examples

data(glasses)

## draw the iso-odds ratio plot with 50% CI and 95% CI,
plotOddsRatio(glasses)

## return the 95% CI information
OddsRatio(glasses)

## draw the iso-odds ratio plot with 50% CI and 95% CI,
## invisibly return the 95% CI information
plotOddsRatio.base(glasses)