So what’s new in googleVis 0.3.2?The default behaviour of the functions
plot.gviscan 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
plotmethod 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 statementWith version 0.3.2 of googleVis
plot.gvisgained the argument
‘tag’, which works similar to the argument of the same name in
print.gvis. By default the tag argument is
plot.gvishas the same behaviour as in the previous versions of googleVis. Change the tag to
plot.gviswill produce the same output as
print.gvis. That means instead of opening a browser window
plot.gviswill return the HTML code of the googleVis chart.
And here is the real trick, if tag is not set explicitly in
plot.gvisthen it will use the value set in
options(gvis.print.tag). Thus, if I set the
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.gvishas been restored.
Here is the example of the updated help file to
plot.gvisand 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 outputThe 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.
URL <- “https://raw.github.com/gist/3968939/f137ecefe6eef3358d2aef89080c06ba061be0c3/KnitMarkdownExample.R"