After last week’s kerfuffle I hope the roll out of googleVis version 0.3.2 will be smooth. To test the water I release this version into the wild here and if it doesn’t get shot down in the next days, then I shall try to upload it to CRAN. I am mindful of the CRAN policy, so please get in touch or add comments below if you find any show stoppers.
So what’s new in googleVis 0.3.2?
The default behaviour of the functions
plot.gvis can be set via
Now this doesn’t sound too exciting but it can be tremendously helpful when you write Markdown files for
knitr. Here is why:
The default googleVis
plot method opens a browser window to display gvis-objects. That’s great when you work with R and googleVis in an interactive and explorative way, but if you like to include the plots into a knitr Markdown file then you would have to change those statements to
print(x, tag="chart"), as explained in an earlier post.
Including googleVis output in knitr with plot statement
With version 0.3.2 of googleVis
plot.gvis gained the argument
'tag', which works similar to the argument of the same name in
print.gvis. By default the tag argument is
plot.gvis has the same behaviour as in the previous versions of googleVis. Change the tag to
plot.gvis will produce the same output as
print.gvis. That means instead of opening a browser window
plot.gvis will return the HTML code of the googleVis chart.
And here is the real trick, if tag is not set explicitly in
plot.gvis then it will use the value set in
options(gvis.print.tag). Thus, if I set the
gvis.plot.tag value to
options() then all following plot statements will return the HTML code of the chart when the file is parsed with
knitr. Set it back to
options(gvis.plot.tag=NULL) and the old behaviour of
plot.gvis has been restored.
Here is the example of the updated help file to
plot.gvis and package vignette. The Markdown and R code is available below. I hope this illustrates the concept clearly.
R Markdown file
R Code to knit HTML output
The code below shows how the Markdown file can be converted into a HTML file and displayed in a browser. If you use RStudio then most of it is happening in the background when you hit the “knit HTML” button.
The following few lines replicate the whole example, sourcing the above gists.