Examples in the vignette of googleVis
--------------------------------------

from [Interactive reports in R with knitr and RStudio]
(http://lamages.blogspot.co.uk/2012/05/interactive-reports-in-r-with-knitr-and.html)

## Geo Chart
```{r, results='asis', message=FALSE}
library(googleVis)
op <- options(gvis.plot.tag='chart') # not enough!
geo <- gvisGeoChart(CityPopularity, locationvar = "City", colorvar = "Popularity", 
    options = list(region = "US", height = 350, displayMode = "markers", colorAxis = "{colors:\n['orange','blue']}"))
print(geo, "chart")
```


## 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)
```