gtree {gWidgets} | R Documentation

## Constructor for widget to display heirarchical dta

### Description

This widget allows tree-like data to be presented. Each node on the tree should be a data frame with the same column structure. The first column is treated like a key, and should be unique. Offspring are specified through a function of the keys which are ancestors. This function returns the data frame to be displayed. Values in the tree can be selected with the mouse. This value can be retrieved through a method, or a handler can be assigned to double click events.

### Usage

    gtree(offspring = NULL, hasOffspring = NULL, offspring.data = NULL,
    col.types = NULL, icon.FUN = NULL, chosencol = 1, multiple = FALSE,
    handler = NULL, action = NULL, container = NULL, ..., toolkit = guiToolkit())

### Arguments

`offspring` | A function to produce a data frame. The first column of the data frame is used as a key. It should be unique, otherwise the updating will not work properly. The `offspring` function has two arguments, the first being the path (the first column of the offspring data frame is the key, and the path is the vector of keys) and the value of `offspring.data`. The data frame can determine whether an entry has offspring, by having the second column be a logical vector, `TRUE` if there is offspring, `FALSE` if not.
`hasOffspring` | Whether an entry has an offspring is determined by a) if this function is non-`NULL` and it returns a `TRUE` value when called on the offspring data frame for this row, b) if the second column of the offspring data frame is a logical vector and for this row is `TRUE`. If this function is `NULL` and the second column is not a logical vector then it is assumed that there are no offspring.
`offspring.data` | Passed to `offspring` function to parameterize that function.
`col.types` | Used to determine the type of column, given as a data frame with 1 or more rows. Otherwise it is determined by first row of offspring data frame. If this can return an empty data frame, then this argument should be given.
`icon.FUN` | An optional function to determine an icon place into the first column. This function gets called with the data in `offspring`, and should return a row vector of length `nrow(offspring)`. The icons are stock icons, and should be referenced by name. The helper function `getStockIcons` list all the available stock icons.
`chosencol` | The column used when requesting the selected row's value. Defaults to first
`multiple` | A logical to determine if multiple selection is allowed. Defaults to `FALSE`
`handler` | Handler for double click events
`action` | Passed to handler
`container` | Optional container to attach widget to.
`...` | Ignored
`toolkit` | Which GUI toolkit to use

### Details

In an abstract sense, these trees are specified by a function which produces the value at a given node from the ancestry of the given node, and a function specifying if a node has offspring.

The `offspring` function determines the displayed data for a certain node. It has signature `(path, offspring.data)`, where the path consists of the ancestors and `offspring.data` is an optional value passed in when the tree object is constructed. This function returns a data frame. Its first column should consist of unique values, as it is treated like a key.

The `hasOffspring` function is called on the return value of `offspring`. It should return a logical indicating which rows have offspring. If this argument is not present, then the second column of the return values of `offspring` are consulted. If these are logical, then they are used to determine if offspring are present. Otherwise, no offspring are assumed.

The `icon.FUN` function is called on the return value of `offspring`. If present, it should return a vector of stock icon names.

The `svalue` method returns the current key. If `index` is set to a column number, that column's value will be returned.

The `"["` method refers to the vector of keys for the selected object.

The `addhandlerdoubleclick` handler can be set to respond to a double click event.

### Examples

    ## Not run:
      ## function to find offspring
      offspring = function(path, user.data=NULL) {
        if(length(path) > 0)
          directory = paste(getwd(),"/",paste(path,sep="/", collapse=""),sep="",collapse="")
        else
          directory = getwd()
        files = file.info(dir(path=directory))[,c(2,1,3)]

        files = cbind(rownames(files), files)
        names(files)[1] = "filename"
        return(files)
     }
     hasOffspring = function(children,user.data=NULL, ...) {
       return(children$isdir)
     }
     icon.FUN = function(children,user.data=NULL, ...) {
       x = rep("file",length= nrow(children))
       x[children$isdir] = "directory"
       return(x)
      }

      gtree(offspring, hasOffspring, icon.FUN = icon.FUN, container=TRUE)
    ## End(Not run)

[Package gWidgets version 0.0-25 Index]