oddsratio {vcd} | R Documentation

## (Log) Odds Ratios

### Description

Computes (log) odds ratios and their asymptotic standard errors for (possibly) stratified data.

### Usage

    oddsratio(x, stratum = NULL, log = TRUE)
    ## S3 method for class 'oddsratio':
    plot(x, conf_level = 0.95, type = "o",
      xlab = "Strata", ylab = NULL, ylim = NULL, whiskers = 0.1, ...)

### Arguments

`x` | a 2 by 2 by ... table.
`stratum` | vector of strata dimensions.
`log` | if `FALSE`, ordinary odds ratios are computed.
`conf_level` | if not `NULL` or `FALSE`, `conf_level`-% confidence intervals are plotted for each data point.
`type` | plot type.
`xlab` | label for the x-axis.
`ylab` | label for the y-axis.
`ylim` | y-axis limits.
`whiskers` | width of the confidence interval whiskers.
`...` | other graphics parameters (see `par`).

### Value

An object of class `"logoddsratio"`, which is simply a vector of (log) odds ratios with dimensionality depending on `stratum`, along with the following attributes:

`ASE` | a numeric vector with the asymptotic standard errors.
`log` | logical indicating whether log odds ratios or common odds ratios are computed.

### Note

The `summary` method prints the standard errors and—for log odds ratios—also computes and prints asymptotic z tests (standardized log odds ratios) and the corresponding p values.

There is a `confint` method for computing confidence intervals for the (log) odds ratios.

The `plot` method plots (log) odds ratios, computed by `oddsratio` for 2 x 2 x k tables, along with confidence intervals.

### Author(s)

David Meyer David.Meyer@R-project.org

### References

M. Friendly (2000), Visualizing Categorical Data. SAS Institute, Cary, NC.

### See Also

`confint`

### Examples

    ## load Coal Miners data
    data(CoalMiners)

    ## compute log odds ratios
    lor <- oddsratio(CoalMiners)
    lor

    ## summary with z tests
    summary(lor)

    ## confidence intervals
    confint(lor)

    ## visualization
    plot(lor,
         xlab = "Age Group",
         main = "Breathelessness and Wheeze in Coal Miners")

    ## add quadratic model
    g <- seq(25, 60, by = 5)
    m <- lm(lor ~ g + I(g^2))
    lines(fitted(m), col = "red")

[Package vcd version 0.9-6 Index]