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Grouped Bar Plots with Error Bars

Source: R/bars.R
bars.Rd

Grouped bar plots with error bars

Usage

bars(
  formula,
  data = NULL,
  heightFun = mean,
  errorFun = ciMean,
  yLabel = NULL,
  xLabels = NULL,
  main = "",
  ylim = NULL,
  barFillColour = NULL,
  barLineWidth = 2,
  barLineColour = "black",
  barSpaceSmall = 0.2,
  barSpaceBig = 1,
  legendLabels = NULL,
  legendDownShift = 0,
  legendLeftShift = 0,
  errorBarLineWidth = 1,
  errorBarLineColour = "grey40",
  errorBarWhiskerWidth = 0.2
)

Arguments

formula

A two-sided formula specifying the response variable and the grouping factors

data

An optional data frame containing the variables

heightFun

The function used to calculate the bar height for a group (default=mean)

errorFun

The function used to calculate the error bar for a group (default=ciMean). No bars drawn if errorFun=FALSE

yLabel

The y-axis label (defaults to the name of the response variable)

xLabels

The x-axis bar labels (defaults to factor labels of the appropriate grouping variable)

main

The plot title

ylim

The y-axis limit: lower bound defaults to 0, default upper bound estimated

barFillColour

The colours to fill the bars (defaults to a rainbow palette with saturation .3)

barLineWidth

The width of the bar border lines (default=2)

barLineColour

The colour of the bar border lines (default="black")

barSpaceSmall

The size of the gap between bars within a cluster, as a proportion of bar width (default=.2)

barSpaceBig

The size of the gap separating clusters of bars, as a proportion of bar width (default=1)

legendLabels

The text for the legend (defaults to factor labels of the appropriate grouping variable). No legends drawn if legendLabels=FALSE or if only one grouping variable is specified

legendDownShift

How far below the top is the legend, as proportion of plot height? (default=0)

legendLeftShift

How far away from the right edge is the legend, as proportion of plot? (default=0)

errorBarLineWidth

The line width for the error bars (default=1)

errorBarLineColour

The colour of the error bars (default="grey40")

errorBarWhiskerWidth

The width of error bar whiskers, as proportion of bar width (default=.2)

Value

Invisibly returns a data frame containing the factor levels, group means and confidence intervals. Note that this function is usually called for its side effects.

Details

Plots group means (or other function, if specified) broken down by one or two grouping factors. Confidence intervals (or other function) are plotted. User specifies a two sided formula of the form response ~ group1 + group2, where response must be numeric and group1 and group2 are factors. The group1 variable defines the primary separation on the x-axis, and the x-axis labels by default print out the levels of this factor. The group2 variable defines the finer grain separation, and the legend labels correspond to the levels of this factor. Note that group2 is optional.