gvisMethods: Print and plot gvis objects
In jburos/GoogleVis: Interface between R and the Google Chart Tools

Description Usage Arguments Details Value Note Author(s) References See Also Examples

Methods to print and plot gvis objects

	
## S3 method for class 'gvis'
print(x, tag=NULL, file = "", ...)
		
## S3 method for class 'gvis'
plot(x, tag=NULL,...)

`x`	An object of class `gvis`, or a HTML file in case of plot.gvis.
`tag`	Default `NULL`. Name tag of the objects to be extracted from a gvis object. If tag is missing then the values of `getOption("gvis.print.tag")`, `getOption("gvis.plot.tag")` will be used for `print.gvis` and `plot.gvis` respectively. A complete list of available tags is given by the command `getOption("gvis.tags")`. The default value of `gvis.print.tag` is `"html"`, which means `print.gvis` will show a complete web page with the visualisation, while the tag `"chart"` will present the code for the visualisation chart only. For more information see the details section. The default tag for `plot.gvis.tag` is `NULL`, which will result in R opening a browser window, while any tag which is not `NULL` will give the same behaviour as `print.gvis`, e.g. `tag='chart'` or setting `options(gvis.plot.tag='chart')` will produce the same output as `print(x, tag='chart')`. This behaviour is particular helpful when googleVis is used in scripts, like `knitr` or `R.rsp`. The plot commands can be used initially in an interactive mode and with one change in `options()` produce the HTML output required for a programmatic run of the script. See the example section below for a `knitr` case study. `plot.gvis` ignores the argument `tag` it `x` is a HTML file name.
`file`	file name. If "" (the default), output will be printed to the standard output connection, the console unless redirected by `sink`.
`...`	arguments passed on to `cat` (`print.gvis`) or `browseURL` (`plot.gvis`).

An object of class "gvis" is a list containing at least the following components (tags):

type

Google visualisation type, e.g. 'MotionChart'

chartid

character id of the chart object. Unique chart ids are required to place several charts on the same page.

html

a list with the building blocks for a page

header

a character string of a html page header: <html>...<body>,

chart

a named character vector of the chart's building blocks:

jsHeader: Opening <script> tag and reference to Google's JavaScript library.
jsData: JavaScript function defining the input data as a JSON object.
jsDrawChart: JavaScript function combing the data with the visualisation API and user options.
jsDisplayChart: JavaScript function calling the handler to display the chart.
jsFooter: End tag </script>.
jsChart: Call of the jsDisplayChart function.
divChart: <div> container to embed the chart into the page.

caption

character string of a standard caption, including data name and chart id.

footer

character string of a html page footer: </body>...</html>, including the used R and googleVis version and link to Google's Terms of Use.

`print.gvis`	None (invisible `NULL`).
`plot.gvis`	Returns the file name invisibly.

The plot command does not open a graphics device in the traditional way. Instead it creates HTML files in a temporary directory and uses the R HTTP server to display the output of a googleVis function locally. A browser with Flash and Internet connection is required. The displayed page includes a link (click on the chart id) to a further page, which shows the code of the chart for the user to copy and paste into her own page.

Markus Gesmann markus.gesmann@gmail.com,

Diego de Castillo decastillo@gmail.com

Please see also the package vignette for the usage of the googleVis package with RApache, brew, knitr and R.rsp.

See also cat, browseURL, createGoogleGadget and gvisMerge for combining charts.

## Show gvis options
sapply(c("gvis.print.tag", "gvis.plot.tag", "gvis.tags"), getOption)

M <- gvisMotionChart(Fruits, "Fruit", "Year")
str(M)
## The output for a complete web page
M

## Access only the plot,
M$html$chart

## wrap it in cat and it becomes more readable,
cat(unlist(M$html$chart))

## or use the print function.
print(M, tag="chart")

## Extract the data as a JavaScript function.
print(M, tag="jsData")

## Display the visualisation.
## A web browser with Internet connection and Flash is required.
plot(M)

## Combine with another chart, e.g. table
tbl <- gvisTable(Fruits, options=list(height=220))
Mtbl <- gvisMerge(M, tbl)
plot(Mtbl)


## Example of using googleVis with knitr and markdown

## Not run: 
## Simple knitr/markdown file with googleVis
knitrRmd <-"
# Markdown example with knitr and googleVis
===========================================
This is a little Markdown example file.
Set the googleVis options first.
In this case change the behaviour of plot.gvis
```{r setOptions, message=FALSE}
library(googleVis)
op <- options(gvis.plot.tag='chart')
```
The following plot statements will automatically return  the HTML
required for the 'knitted' output. 

## Combo chart
```{r ComboExample, results='asis', tidy=FALSE}
## Add the mean
CityPopularity$Mean=mean(CityPopularity$Popularity)
CC <- gvisComboChart(CityPopularity, xvar='City',
          yvar=c('Mean', 'Popularity'),
          options=list(seriesType='bars',
                       width=450, height=300,
                       title='City Popularity',
                       series='{0: {type:\"line\"}}'))
plot(CC)
```
Example of gvisComboChart with R code shown above.

## Place two charts next to each other
```{r gvisMergeExample, results='asis', echo=FALSE}
Geo <- gvisGeoChart(Exports, locationvar='Country', colorvar='Profit', 
                    options=list(height=300, width=350)) 
Tbl <- gvisTable(Exports, options=list(height=300, width=200))
plot(gvisMerge(Geo, Tbl, horizontal=TRUE))
``````
Example of a gvisGeoChart with gvisTable and R code hidden.

## Motion Chart
```{r MotionChartExample, results='asis', tidy=FALSE}
M <- gvisMotionChart(Fruits, 'Fruit', 'Year',
         options=list(width=400, height=350))
plot(M)
```
Please note that the Motion Chart is only displayed when hosted on a
web server, or is placed in a directory which has been added to the 
trusted sources in the [security settings of Macromedia]
(http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager04.html). 
See the googleVis package vignette for more details. 

```{r resetOptions}
## Set options back to original options
options(op)
```
"

## Write the content of knitrRmd into a Rmd-file, knit it and convert it
## into a html output. Finally show the file with the R-help http
## server, this will ensure that also the motion chart is visible.

library(knitr)
library(markdown)

wd <- getwd()
setwd(tempdir())
fn=tempfile()
fn.Rmd <- paste(fn, ".Rmd", sep="")
fn.md <- paste(fn, ".md", sep="")
fn.html <- paste(fn, "-out.html", sep="") 
## Write R Markdown into a file
cat(knitrRmd, file=fn.Rmd)
render_markdown()
knit(fn.Rmd, fn.md)
knit2html(fn.md)

## Open output in browser
## Use plot.gvis which will use the R-help http server
## The URL will start with http://127.0.0.1...
## The HTML file will be copied into a temporary directory
plot.gvis(fn.html)
## Compare to browseURL, its URL will start with file://... the motion
## chart is unlikely to be displayed because of Flash security
## settings. See the googleVis vignette for more details. 
browseURL(fn.html)
setwd(wd)

## End(Not run)

## Not run: 
## Updating the data of an existing googleVis web page

## Suppose you have an existing web page in which you embedded a
## motion chart with the id "mtnc".
## Now you have a new set of data, but you would like to avoid
## touching the html file again.
## The idea is to write the data and JavaScript functions into separate
## files and to refer to these in the html page.

## In this example we call the chart id "mtnc"
## To display the example we use the R HTTP server again, and
## write the files into a temp directory

myChartID <- "mtnc"
## baseURL should reflect your web address, e.g. http://myHomePage.com
baseURL <- sprintf("http://127.0.0.1:%s/custom/googleVis", tools:::httpdPort)
wwwdir <- tempdir() ## the www repository on your computer

  
## Create a motion chart
M=gvisMotionChart(Fruits, "Fruit", "Year", chartid=myChartID)

## Here is our plot again
plot(M)

## Write the data and functions into separate files:
cat(M$html$chart['jsData'], file=file.path(wwwdir, "gvisData.js"))
cat(M$html$chart[c('jsDrawChart', 'jsDisplayChart', 'jsChart')], 
			    file=file.path(wwwdir, "gvisFunctions.js"))

  
## Create a html page with reference to the above
## JavaScript files
  
html <- sprintf('
<html>
  <head>
  <script type="text/javascript" src="http://www.google.com/jsapi">
  </script>
  <script type="text/javascript" src="%s/gvisFunctions.js"></script>
  <script type="text/javascript" src="%s/gvisData.js"></script>
  <script type="text/javascript">
  displayChart%s()
  </script>
  </head>
  <body>
  <div id="%s" style="width: 600px; height: 500px;"></div>
  </body>
  </html>
  ', baseURL, baseURL, myChartID, myChartID)
  
## Write html scaffold into a file
cat(html, file=file.path(wwwdir, paste("Chart", myChartID, ".html", sep="")))

## Display the result via
URL <- paste(baseURL,"/Chart", myChartID, ".html", sep="")
browseURL(URL)

## Update the data, say the data should have shown North and South
## instead of East and West as a location  
FruitsUpdate <- Fruits
levels(FruitsUpdate$Location)=c("North", "South")

Mupdate=gvisMotionChart(FruitsUpdate, "Fruit", "Year", chartid=myChartID)

## Only update the file gvisData.js:
cat(Mupdate$html$chart['jsData'], file=file.path(wwwdir, "gvisData.js"))

## Redisplay the chart with the updated data
browseURL(URL)


## End(Not run)