R: Constructor for widget to display tabular data

gtable {gWidgets} | R Documentation

## Constructor for widget to display tabular data

### Description

This widget displays either a vector, matrix or data frame in a tabular format. The main usage is for user selection of a row or rows.

### Usage

    gtable(items, multiple = FALSE, chosencol = 1, icon.FUN = NULL,
    filter.column = NULL, filter.labels = NULL, filter.FUN = NULL,
    handler = NULL, action = NULL, container = NULL, ..., toolkit = guiToolkit())

### Arguments

`items` | A vector, matrix or data frame to be displayed. A vector and matrix is coerced into a data frame.
`multiple` | A logical. If `TRUE` multiple lines can be selected
`chosencol` | By default, only the value in this column is returned by the `svalue` method.
`icon.FUN` | If given, this function is applied to the data frame to be shown. It should return a vector of stock icon names
`filter.column` | If not `NULL` a filter by droplist is given which can be used to filter the displayed values shown using the values in this column.
`filter.labels` | If more complex filtering is desired then this argument populates the values of the combobox and the `filter.FUN` argument is used to specify a function to interpret these values.
`filter.FUN` | Either a function with signature `(obj, filter.by)` to specify a vector of logical values indicating which rows should be shown or the character "manual" in which filtering is done directly through the `visible` method and not through a popup box
`handler` | Called on a double click event
`action` | Passed to handler
`container` | Optional container to attach widget to
`...` | ignored
`toolkit` | Which GUI toolkit to use

### Details

The `svalue` method returns the selected value(s). By default, only the value(s) in the chosen column are returned. Use the argument `drop=FALSE` to return the entire row. To return the row index, use the argument `index=TRUE`. This index refers to the whole data store, not just the visible portion when filtering is being used.

The `"["` notion treats the object like a data frame. When filtering, this notation refers to the entire data frame, not the visible data frame. The comment about the returned index by `svalue` can be described by the fact that `obj[svalue(obj,index=TRUE), ]` should be the same value as `svalue(obj)`.

Assignment via `"[<-"` is possible with limitations imposed by the toolkits. The graphical display of tabular matter is usually done, similar to data frames, in terms of columns each having the same type. For some toolkits, all values are converted to characters, for others, the type must be maintained. In R, coercion of types may occur when assigning to a data frame, but this won't be so with the underlying toolkit widget. To be portable across toolkits, the column type should not change during assignment, nor should the number of rows be reduced.

In particular, assignment with `"[<-"` for factors can cause warnings if the values are not in the factor's levels. When the value being assigned is a matrix there is a coercion to a data frame which may change the type.

The `visible` and `visible<-` methods refer to which rows of the data store are visible in the widget. These are specified by a vector of class logical. This may be used when there is filtering, not sorting. The value returned by `svalue` is a logical vector of length given by the number of rows of the data store, with `TRUE` indicating that the row is displayed. When setting the visibility of a row through `svalue` the vector of values should have the same length as the number of rows, otherwise recycling occurs. (So `visible(obj) <- TRUE` will work to display all the rows.)

The `length` method returns the length of the underlying data store.

The `dim` method returns the dimension of the underlying data store.

The `names` method returns the names of the underlying data store.

The `names<-` method can be used to set the names of the underlying data store and the values displayed in the column headers of the widget.

Row names are ignored in the display of this widget.

A single click is used for selection of a value.

The `addHandlerDoubleclick` handler can be used to define a callback to respond to a double click event.

### See Also

See also `gtree` for displaying tree-like data and `gdf` for tabular data meant to be edited

### Examples

    ## Not run:
      ## example to select CRAN mirror
      m <- getCRANmirrors()[,c(1,4)]
      setCRAN <- function(URL) { ## see chooseCRANmirror
        repos = getOption("repos")
        repos["CRAN"] <- gsub("/$", "", URL)
        options(repos=repos)
      }
      w <- gwindow("gtable example",width=400)
      gp <- ggroup(horizontal=FALSE, container=w)
      tab <- gtable(m, chosencol = 2, container=gp, expand=TRUE,
           handler = function(h,...) setCRAN(svalue(h$obj)))
      bg <- ggroup(container=gp)
      addSpring(bg)
      gbutton("dismiss", container=bg, handler = function(h,...) dispose(w))

      ## an example with icons.
      ## Select variables from a data frame

      ## find icons by class
      icon.FUN <- function(items) {
        dfName <- svalue(cb)
        df <- try(get(dfName, envir=.GlobalEnv), silent=TRUE)
        if(inherits(df,"try-error"))
          return(rep(NULL,dim(items)[1]))
        if(is.data.frame(items))
          items <- items[,1, drop=TRUE]
        sapply(items, function(i) {
          class(df[,i])[1]
        })
      }
      ## list data frames in an environment
      lsDF <- function(envir=.GlobalEnv) {
        varNames <- ls(envir=envir)
        dfs <- sapply(varNames, function(i) inherits(get(i,envir=envir),"data.frame"))
        varNames[dfs]
      }
      ## set up GUI
      w <- gwindow("Select variables",width=250)
      g <- ggroup(horizontal=FALSE, container=w)
      l <- glabel("Data frame", container=g)
      cb <- gcombobox(lsDF(), container=g)
      blankDF = data.frame(variables=character(0), stringsAsFactors=FALSE)
      tbl <- gtable(blankDF, icon.FUN=icon.FUN, container=g, expand=TRUE)
      ## add handlers
      addHandlerChanged(cb, handler <- function(h,...) {
        dfName <- svalue(h$obj)
        dfNames <- names(get(dfName,envir=.GlobalEnv))
        tbl[,] <- data.frame(variables=dfNames, stringsAsFactors=FALSE)
      })
      addHandlerClicked(tbl, handler = function(h,...) {
        cat("Do something with",svalue(cb),"::", svalue(h$obj),"\n")
      })

    ## End(Not run)

[Package gWidgets version 0.0-54 Index]