R: Label Attribute of an Object

label {Hmisc} | R Documentation

## Label Attribute of an Object

### Description

`label(x)` retrieves the `label` attribute of `x`. `label(x) <- "a label"` stores the label attribute, and also puts the class `labelled` as the first class of `x` (for S-Plus this class is not used and methods for handling this class are not defined so the `"label"` and `"units"` attributes are lost upon subsetting). The reason for having this class is so that the subscripting method for `labelled`, `[.labelled`, can preserve the `label` attribute in S. Also, the `print` method for `labelled` objects prefaces the print with the object's `label` (and `units` if there). If the variable is also given a `"units"` attribute using the `units` function, subsetting the variable (using `[.labelled`) will also retain the `"units"` attribute.

`label` can optionally append a `"units"` attribute to the string, and it can optionally return a string or expression (for R's `plotmath` facility) suitable for plotting. `labelPlotmath` is a function that also has this function, when the input arguments are the `'label'` and `'units'` rather than a vector having those attributes. When `plotmath` mode is used to construct labels, the `'label'` or `'units'` may contain math expressions but they are typed verbatim if they contain percent signs, blanks, or underscores. `labelPlotmath` can optionally create the expression as a character string, which is useful in building `ggplot` commands.

For `Surv` objects, `label` first looks to see if there is an overall `"label"` attribute for the object, then it looks for saved attributes that `Surv` put in the `"inputAttributes"` object, looking first at the `event` variable, then `time2`, and finally `time`. You can restrict the looking by specifying `type`.

`labelLatex` constructs suitable LaTeX labels a variable or from the `label` and `units` arguments, optionally right-justifying `units` if `hfill=TRUE`. This is useful when making tables when the variable in question is not a column heading. If `x` is specified, `label` and `units` values are extracted from its attributes instead of from the other arguments.

`Label` (actually `Label.data.frame`) is a function which generates S source code that makes the labels in all the variables in a data frame easy to edit.

`llist` is like `list` except that it preserves the names or labels of the component variables in the variables `label` attribute. This can be useful when looping over variables or using `sapply` or `lapply`. By using `llist` instead of `list` one can annotate the output with the current variable's name or label. `llist` also defines a `names` attribute for the list and pulls the `names` from the arguments' expressions for non-named arguments.

`prList` prints a list with element names (without the dollar sign as in default list printing) and if an element of the list is an unclassed list with a name, all of those elements are printed, with titles of the form "primary list name : inner list name". This is especially useful for Rmarkdown html notebooks when a user-written function creates multiple html and graphical outputs to all be printed in a code chunk. Optionally the names can be printed after the object, and the `htmlfig` option provides more capabilities when making html reports. `prList` does not work for regular html documents.

`putHfig` is similar to `prList` but for a single graphical object that is rendered with a `print` method, making it easy to specify long captions, and short captions for the table of contents in HTML documents. Table of contents entries are generated with the short caption, which is taken as the long caption if there is none. One can optionally not make a table of contents entry. If argument `table=TRUE` table captions will be produced instead. Using `expcoll`, `markupSpecs` `html` function `expcoll` will be used to make tables expand upon clicking an arrow rather than always appear.

`putHcap` is like `putHfig` except it is for figures only, and assumes that users render the graphics outside of the `putHcap` call. This allows things to work in ordinary html documents.

`plotmathTranslate` is a simple function that translates certain character strings to character strings that can be used as part of R `plotmath` expressions. If the input string has a space or percent inside, the string is surrounded by a call to `plotmath`'s `paste` function.

`as.data.frame.labelled` is a utility function that is called by `[.data.frame`. It is just a copy of `as.data.frame.vector`. `data.frame.labelled` is another utility function, that adds a class `"labelled"` to every variable in a data frame that has a `"label"` attribute but not a `"labelled"` class.

`relevel.labelled` is a method for preserving `label`s with the `relevel` function.

`reLabelled` is used to add a `'labelled'` class back to variables in data frame that have a 'label' attribute but no 'labelled' class. Useful for changing `cleanup.import()`'d S-Plus data frames back to general form for R and old versions of S-Plus.

### Usage

    label(x, default=NULL, ...)

    ## Default S3 method:
    label(x, default=NULL, units=plot, plot=FALSE,
          grid=FALSE, html=FALSE, ...)

    ## S3 method for class 'Surv'
    label(x, default=NULL, units=plot, plot=FALSE,
          grid=FALSE, html=FALSE, type=c('any', 'time', 'event'), ...)

    ## S3 method for class 'data.frame'
    label(x, default=NULL, self=FALSE, ...)

    label(x, ...) <- value

    ## Default S3 replacement method:
    label(x, ...) <- value

    ## S3 replacement method for class 'data.frame'
    label(x, self=TRUE, ...) <- value

    labelPlotmath(label, units=NULL, plotmath=TRUE, html=FALSE, grid=FALSE,
                  chexpr=FALSE)

    labelLatex(x=NULL, label='', units='', size='smaller[2]',
               hfill=FALSE, bold=FALSE, default='', double=FALSE)

    ## S3 method for class 'labelled'
    print(x, ...)   ## or x - calls print.labelled

    Label(object, ...)

    ## S3 method for class 'data.frame'
    Label(object, file='', append=FALSE, ...)

    llist(..., labels=TRUE)

    prList(x, lcap=NULL, htmlfig=0, after=FALSE)

    putHfig(x, ..., scap=NULL, extra=NULL, subsub=TRUE, hr=TRUE,
            table=FALSE, file='', append=FALSE, expcoll=NULL)

    putHcap(..., scap=NULL, extra=NULL, subsub=TRUE, hr=TRUE,
            file='', append=FALSE)

    plotmathTranslate(x)

    data.frame.labelled(object)

    ## S3 method for class 'labelled'
    relevel(x, ...)

    reLabelled(object)

    combineLabels(...)

### Arguments

`x` | any object (for `plotmathTranslate` is a character string). For `relevel` is a `factor` variable. For `prList` is a named list. For `putHfig` is a graphical object for which a `print` method will render the graphic (e.g., a `ggplot2` or `plotly` object).
`self` | lgoical, where to interact with the object or its components
`units` | set to `TRUE` to append the `'units'` attribute (if present) to the returned label. The `'units'` are surrounded by brackets. For `labelPlotmath` and `labelLatex` is a character string containing the units of measurement. When `plot` is `TRUE`, `units` defaults to `TRUE`.
`plot` | set to `TRUE` to return a label suitable for R's `plotmath` facility (returns an expression instead of a character string) if R is in effect. If `units` is also `TRUE`, and if both `'label'` and `'units'` attributes are present, the `'units'` will appear after the label but in smaller type and will not be surrounded by brackets.
`default` | if `x` does not have a `'label'` attribute and `default` (a character string) is specified, the label will be taken as `default`. For `labelLatex` the `default` is the name of the first argument if it is a variable and not a label.
`grid` | Currently R's `lattice` and `grid` functions do not support `plotmath` expressions for `xlab` and `ylab` arguments. When using `lattice` functions in R, set the argument `grid` to `TRUE` so that `labelPlotmath` can return an ordinary character string instead of an expression.
`html` | set to `TRUE` to use HTML formatting instead of plotmath expressions for constructing labels with units
`type` | for `Surv` objects specifies the type of element for which to restrict the search for a label
`label` | a character string containing a variable's label
`plotmath` | set to `TRUE` to have `labelMathplot` return an expression for plotting using R's `plotmath` facility. If R is not in effect, an ordinary character string is returned.
`chexpr` | set to `TRUE` to have `labelPlotmath` return a character string of the form `"expression(...)"`
`size` | LaTeX size for `units`. Default is two sizes smaller than `label`, which assumes that the LaTeX `relsize` package is in use.
`hfill` | set to `TRUE` to right-justify `units` in the field. This is useful when multiple labels are being put into rows in a LaTeX `tabular` environment, and will cause a problem if the label is used in an environment where `hfill` is not appropriate.
`bold` | set to `TRUE` to have `labelLatex` put the `label` in bold face.
`double` | set to `TRUE` to represent backslash in LaTeX as four backslashes in place of two. This is needed if, for example, you need to convert the result using `as.formula`
`value` | the label of the object, or "".
`object` | a data frame
`...` | a list of variables or expressions to be formed into a `list`. Ignored for `print.labelled`. For `relevel` is the `level` (a single character string) to become the new reference (first) category. For `putHfig` and `putHcap` represents one or more character strings that are pasted together, separated by a blank.
`file` | the name of a file to which to write S source code. Default is `""`, meaning standard output. For `putHcap`, set `file` to `FALSE` to return a character vector instead of writing to `file`.
`append` | set to `TRUE` to append code generated by `Label` to file `file`. Also used for `putHfig, putHcap`.
`labels` | set to `FALSE` to make `llist` ignore the variables' `label` attribute and use the variables' names.
`lcap` | an optional vector of character strings corresponding to elements in `x` for `prList`. These contain long captions that do not appear in the table of contents but which are printed right after the short caption in the body, in the same font.
`htmlfig` | for `prList` set to `1` to use HTML markup by running the object names through `markupSpecs$html$cap` for figure captions. Set `htmlfig=2` to also preface the figure caption with `"### "` so that it will appear in the table of contents.
`after` | set to `TRUE` to have `prList` put names after the printed object instead of before
`scap` | a character string specifying the short (or possibly only) caption.
`extra` | an optional vector of character strings. When present the long caption will be put in the first column of an HTML table and the elements of `extra` in subsequent columns. This allows extra information to appear in the long caption in a way that is right-justified to the right of the flowing caption text.
`subsub` | set to `FALSE` to suppress `"### "` from being placed in front of the short caption.
`hr` | applies if a caption is present. Specify `FALSE` to not put a horizontal line before the caption and figure.
`table` | set to `TRUE` to produce table captions instead of figure captions
`expcoll` | character string to be visible, with a clickable arrow following to allow initial hiding of a table and its captions. Cannot be used with `table=FALSE`.

### Value

`label` returns the label attribute of x, if any; otherwise, "". `label` is used most often for the individual variables in data frames. The function `sas.get` copies labels over from SAS if they exist.

### See Also

`sas.get`, `describe`

### Examples

    age <- c(21,65,43)
    y   <- 1:3
    label(age) <- "Age in Years"
    plot(age, y, xlab=label(age))

    data <- data.frame(age=age, y=y)
    label(data)

    label(data, self=TRUE) <- "A data frame"
    label(data, self=TRUE)

    x1 <- 1:10
    x2 <- 10:1
    label(x2) <- 'Label for x2'
    units(x2) <- 'mmHg'
    x2
    x2[1:5]
    dframe <- data.frame(x1, x2)
    Label(dframe)

    labelLatex(x2, hfill=TRUE, bold=TRUE)
    labelLatex(label='Velocity', units='m/s')

    ##In these examples of llist, note that labels are printed after
    ##variable names, because of print.labelled
    a <- 1:3
    b <- 4:6
    label(b) <- 'B Label'
    llist(a,b)
    llist(a,b,d=0)
    llist(a,b,0)

    w <- llist(a, b>5, d=101:103)
    sapply(w, function(x){
      hist(as.numeric(x), xlab=label(x))
      # locator(1)   ## wait for mouse click
    })

    # Or: for(u in w) {hist(u); title(label(u))}

[Package Hmisc version 4.2-0 Index]