# Easy Creation of Tables of Percentages

### Description

The generic function `percentages`

and its methods
create one- or multidimensional tables of percentages. As such,
the function `percentages`

can be viewed as a convenience
interface to `prop.table`

. However, it also
allows to obtain standard errors and confidence intervals.

### Usage

1 2 3 4 5 6 7 8 9 10 11 | ```
percentages(obj, ...)
## S3 method for class 'table'
percentages(obj,
by=NULL, which=NULL, se=FALSE, ci=FALSE, ci.level=.95, ...)
## S3 method for class 'formula'
percentages(obj,
data=parent.frame(), weights=NULL, ...)
## S3 method for class 'percentage.table'
as.data.frame(x, ...)
## S3 method for class 'xpercentage.table'
as.data.frame(x, ...)
``` |

### Arguments

`obj` |
an object; a contingency table or a formula. If it is a formula, its left-hand side determines the factor or combination of factors for which percentages are computed while its right-hand side determines the factor or combination of factors that define the groups within which percentages are computed. |

`by` |
a character vector with the names of the factor variables that define the groups within which percentages are computed. Percentages sum to 100 within combination of levels of these factors. |

`which` |
a character vector with the names of the factor variables for which percentages are computed. |

`se` |
a logical value; determines whether standard errors are computed. |

`ci` |
a logicla value; determines whether confidence intervals are computed. Note that the confidence intervals are for infinite (or very large) populations. |

`ci.level` |
a numerical value, the required confidence level of the confidence intervals. |

`data` |
a contingency table (an object that inherits from "table") or a data frame or an object coercable into a data frame. |

`weights` |
an optional character string with the name of a variable containing weights. |

`x` |
an object coerced into a data frame. |

`...` |
Further arguments, ignored. |

### Value

An array that inherits classes "percentage.table" and "table". If
`percentages`

was called with `se=TRUE`

or `ci=TRUE`

then the result additionally inherits class "xpercentage.table".

### Examples

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 | ```
# Two equivalent ways to create the same table
100*prop.table(UCBAdmissions)
percentages(UCBAdmissions)
# Three equivalent ways to create the same table
100*prop.table(UCBAdmissions,c(2,3))
(p0 <- percentages(UCBAdmissions,by=c("Gender","Dept")))
percentages(UCBAdmissions,which="Admit")
# Percentage table as data frame
as.data.frame(p0)
# Three equivalent ways to create the same table
100*prop.table(margin.table(UCBAdmissions,c(1,2)),2)
percentages(UCBAdmissions,which="Admit",by="Gender")
percentages(Admit~Gender,data=UCBAdmissions)
# Three equivalent ways to create the same table
100*prop.table(margin.table(UCBAdmissions,c(1,3)),2)
percentages(Admit~Dept,data=UCBAdmissions)
percentages(Admit~Dept,data=as.data.frame(UCBAdmissions),
weights="Freq")
# Standard errors and confidence intervals
percentages(Admit~Dept,data=UCBAdmissions,se=TRUE)
percentages(Admit~Dept,data=UCBAdmissions,ci=TRUE)
(p<- percentages(Admit~Dept,data=UCBAdmissions,ci=TRUE,se=TRUE))
# An extended table of percentages as data frame
as.data.frame(p)
``` |

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