bystats {Hmisc} | R Documentation

## Statistics by Categories

### Description

For any number of cross-classification variables, `bystats` returns a matrix with the sample size, number missing `y`, and `fun(non-missing y)`, with the cross-classifications designated by rows. Uses Harrell's modification of the `interaction` function to produce cross-classifications. The default `fun` is `mean`, and if `y` is binary, the mean is labeled as `Fraction`. There is a `print` method as well as a `latex` method for objects created by `bystats`. `bystats2` handles the special case in which there are 2 classifcation variables, and places the first one in rows and the second in columns. The `print` method for `bystats2` uses the S-Plus `print.char.matrix` function to organize statistics for cells into boxes.

### Usage

    bystats(y, ..., fun, nmiss, subset)
    ## S3 method for class 'bystats':
    print(x, ...)
    ## S3 method for class 'bystats':
    latex(object, title, caption, rowlabel, ...)
    bystats2(y, v, h, fun, nmiss, subset)
    ## S3 method for class 'bystats2':
    print(x, abbreviate.dimnames=FALSE,
       prefix.width=max(nchar(dimnames(x)[[1]])), ...)
    ## S3 method for class 'bystats2':
    latex(object, title, caption, rowlabel, ...)

### Arguments

`y` | a binary, logical, or continuous variable or a matrix or data frame of such variables. If `y` is a data frame it is converted to a matrix. If `y` is a data frame or matrix, computations are done on subsets of the rows of `y`, and you should specify `fun` so as to be able to operate on the matrix. For matrix `y`, any column with a missing value causes the entire row to be considered missing, and the row is not passed to `fun`.
`...` | For `bystats`, one or more classifcation variables separated by commas. For `print.bystats`, options passed to `print.default` such as `digits`. For `latex.bystats`, and `latex.bystats2`, options passed to `latex.default` such as `digits`. If you pass `cdec` to `latex.default`, keep in mind that the first one or two positions (depending on `nmiss`) should have zeros since these correspond with frequency counts.
`v` | vertical variable for `bystats2`. Will be converted to `factor`.
`h` | horizontal variable for `bystats2`. Will be converted to `factor`.
`fun` | a function to compute on the non-missing `y` for a given subset. You must specify `fun=` in front of the function name or definition. `fun` may return a single number or a vector or matrix of any length. Matrix results are rolled out into a vector, with names preserved. When `y` is a matrix, a common `fun` is `function(y) apply(y, 2, ff)` where `ff` is the name of a function which operates on one column of `y`.
`nmiss` | A column containing a count of missing values is included if `nmiss=TRUE` or if there is at least one missing value.
`subset` | a vector of subscripts or logical values indicating the subset of data to analyze
`abbreviate.dimnames` | set to `TRUE` to abbreviate `dimnames` in output
`prefix.width` | see `print.char.matrix` if using S-Plus
`title` | `title` to pass to `latex.default`. Default is the first word of the character string version of the first calling argument.
`caption` | caption to pass to `latex.default`. Default is the `heading` attribute from the object produced by `bystats`.
`rowlabel` | `rowlabel` to pass to `latex.default`. Default is the `byvarnames` attribute from the object produced by `bystats`. For `bystats2` the default is `""`.
`x` | an object created by `bystats` or `bystats2`
`object` | an object created by `bystats` or `bystats2`

### Value

for `bystats`, a matrix with row names equal to the classification labels and column names `N, Missing, funlab`, where `funlab` is determined from `fun`. A row is added to the end with the summary statistics computed on all observations combined. The class of this matrix is `bystats`. For `bystats`, returns a 3-dimensional array with the last dimension corresponding to statistics being computed. The class of the array is `bystats2`.

### Side Effects

`latex` produces a `.tex` file.

### Author(s)

Frank Harrell
Department of Biostatistics
Vanderbilt University
f.harrell@vanderbilt.edu

### See Also

`interaction`, `cut`, `cut2`, `latex`, `print.char.matrix`, `translate`

### Examples

    ## Not run:
    bystats(sex==2, county, city)
    bystats(death, race)
    bystats(death, cut2(age,g=5), race)
    bystats(cholesterol, cut2(age,g=4), sex, fun=median)
    bystats(cholesterol, sex, fun=quantile)
    bystats(cholesterol, sex, fun=function(x)c(Mean=mean(x),Median=median(x)))
    latex(bystats(death,race,nmiss=FALSE,subset=sex=="female"), digits=2)
    f <- function(y) c(Hazard=sum(y[,2])/sum(y[,1]))
    # f() gets the hazard estimate for right-censored data from exponential dist.
    bystats(cbind(d.time, death), race, sex, fun=f)
    bystats(cbind(pressure, cholesterol), age.decile,
            fun=function(y) c(Median.pressure   =median(y[,1]),
                              Median.cholesterol=median(y[,2])))
    y <- cbind(pressure, cholesterol)
    bystats(y, age.decile,
            fun=function(y) apply(y, 2, median))   # same result as last one
    bystats(y, age.decile, fun=function(y) apply(y, 2, quantile, c(.25,.75)))
    # The last one computes separately the 0.25 and 0.75 quantiles of 2 vars.
    latex(bystats2(death, race, sex, fun=table))
    ## End(Not run)

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