R: Widgets to allow selection from a vector of items

gcombobox {gWidgets} | R Documentation

## Widgets to allow selection from a vector of items

### Description

A combobox allows selection of a value from a list of items using a popup menu. Additionally, the widget can combine a text entry widget for user input outside of the pre-set list of items. A combobox is useful for selection from a moderate size of items (2-30, say). For smaller sets of items, a radio button group is a possibility, for larger sets of items, a scrollable (and perhaps searchable) table may be preferred.

### Usage

    gcombobox(items, selected = 1, editable = FALSE, coerce.with=NULL, handler = NULL,
        action = NULL, container = NULL, ..., toolkit = guiToolkit())

    gdroplist(items, selected = 1, editable = FALSE, coerce.with=NULL, handler = NULL,
        action = NULL, container = NULL, ..., toolkit = guiToolkit())

### Arguments

`items` | Vector of values to select from. This may also be a data frame, in which case the first column is the vector of values, the second (if present) indicates a stock icon to display with the item (not all toolkits), and the third (if present) will indicate a tooltip to display (not all toolkits).
`selected` | For gradio the initial selected value (as an index) For a drop list, the first selected value. Use 0 to leave blank
`editable` | A logical indicating if the user can add an entry to the list of available answers
`coerce.with` | Apply this function to selected value before returning
`handler` | Called when selection is changed
`action` | Passed to handler when called.
`container` | Optional container to attach widget to
`...` | Passed to `add` method of container
`toolkit` | Which GUI toolkit to use

### Details

The initial `items` can be a vector or a data frame. Not all tool kits do something with the extra columns in the data frame.

The `svalue` method returns the selected value by name. Assume the value is a character vector. Use the `coerce.with` argument to return a value of a different type. If the extra argument `index=TRUE` is specified, the index of the selected value is given.

The `svalue<-` method can be used to set the selected value. This is done my name or if the argument `index=TRUE` is given by index. The value can be a data frame, in which case the first column is used to match against the current items.

The `"["` method refers to the vector defining the items.

The `"[<-"` method can be used to change the vector defining the items.

The `"length"` method returns the number of items.

For `gcombobox` the argument `editable=TRUE` adds a text-edit box where the user can type in a selection. By default this value is returned as a character by `svalue`. Use `coerce.with` to coerce this prior to returning.

### See Also

A combobox is one of several ways to select a value of a set of items. See also `gcheckbox`, `gradio`, `gcheckboxgroup`, and `gtable`.

Methods for gComponent objects are detailed in `gWidgets-methods`.

Event Handlers are detailed in `gWidgets-handlers`.

### Examples

    ## Not run:
      flavors <- c("vanilla", "chocolate", "strawberry")

      f <- function(h,...) print(
          paste("Yum",
          paste(svalue(h$obj),collapse=" and "),
          sep = " "))

      w <- gwindow("combobox example")
      gp <- ggroup(container=w)
      glabel("Favorite flavor:", container=gp)
      cb <- gcombobox(flavors, editable=TRUE, container=gp, handler=f)

      svalue(cb) <- "vanilla"
      svalue(cb)
      cbg[3] <- "raspberry"

    ## End(Not run)

[Package gWidgets version 0.0-54 Index]