Google Bar Chart with R barchart gvisBarChart

The gvisBarChart function reads a data.frame and creates text output referring to the Google Visualisation API, which can be included into a web page, or as a stand-alone page. The actual chart is rendered by the web browser using SVG or VML.

Usage

gvisBarChart(data, xvar = "", yvar = "", options = list(), chartid)

Arguments

data

a data.frame to be displayed as a bar chart

xvar

name of the character column which contains the category labels for the x-axes.

yvar

a vector of column names of the numerical variables to be plotted. Each column is displayed as a separate bar/column.

options

list of configuration options, see:

https://developers.google.com/chart/interactive/docs/gallery/barchart#Configuration_Options

The parameters can be set via a named list. The parameters have to map those of the Google documentation.

Boolean arguments are set to either TRUE or FALSE, using the R syntax.
Google API parameters with a single value and with names that don't include a "." are set like one would do in R, that is options=list(width=200, height=300). Exceptions to this rule are the width and height options for gvisAnnotatedTimeLine and gvisAnnotationChart. For those two functions, width and height must be character strings of the format "Xpx", where X is a number, or "automatic". For example, options=list(width="200px", height="300px").
Google API parameters with names that don't include a ".", but require multivalues are set as a character, wrapped in "[ ]" and separated by commas, e.g. options=list(colors="['#cbb69d', '#603913', '#c69c6e']")
Google API parameters with names that do include a "." present parameters with several sub-options and have to be set as a character wrapped in "{ }". The values of those sub-options are set via parameter:value. Boolean values have to be stated as 'true' or 'false'. For example the Google documentaion states the formating options for the vertical axis and states the parameter as vAxis.format. Then this paramter can be set in R as:options=list(vAxis="\{format:'#,###%'\}").
If several sub-options have to be set, e.g. titleTextStyle.color, titleTextStyle.fontName and titleTextStyle.fontSize, then those can be combined in one list item such as:options=list(titleTextStyle="\{color:'red', fontName:'Courier', fontSize:16\}")
paramters that can have more than one value per sub-options are wrapped in "[ ]". For example to set the labels for left and right axes use:options=list(vAxes="[\{title:'val1'\}, \{title:'val2'\}]")
gvis.editor a character label for an on-page button that opens an in-page dialog box enabling users to edit, change and customise the chart. By default no value is given and therefore no button is displayed.

For more details see the Google API documentation and the R examples below.

chartid

character. If missing (default) a random chart id will be generated based on chart type and tempfile

Value

gvisBarChart returns list of class

"gvis" and "list". An object of class "gvis" is a list containing at least the following components:

type

Google visualisation type

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.

References

Google Chart Tools API: https://developers.google.com/chart/interactive/docs/gallery/barchart

Author

Markus Gesmann markus.gesmann@gmail.com,

Diego de Castillo decastillo@gmail.com

Examples


## Please note that by default the googleVis plot command
## will open a browser window and requires an internet
## connection to display the visualisation.

df <- data.frame(country=c("US", "GB", "BR"), 
                           val1=c(1,3,4), 
                           val2=c(23,12,32))

## Bar chart
Bar1 <- gvisBarChart(df, xvar="country", yvar=c("val1", "val2"))
plot(Bar1)

## Stacked bar chart
Bar2 <- gvisBarChart(df, xvar="country", yvar=c("val1", "val2"),
     options=list(isStacked=TRUE))
plot(Bar2)


## Add a customised title and change width of bars
Bar3 <- gvisBarChart(df, xvar="country", yvar=c("val1", "val2"),
             options=list(title="Hello World",
                          titleTextStyle="{color:'red',fontName:'Courier',fontSize:16}",
                          bar="{groupWidth:'100%'}"))
plot(Bar3)

if (FALSE) {
## Change x-axis to percentages
Bar4 <- gvisBarChart(df, xvar="country", yvar=c("val1", "val2"),
                       options=list(hAxis="{format:'#,###%'}"))
plot(Bar4)

## The following example reads data from a Wikipedia table and displays
## the information in a bar chart.
## We use the readHMLTable function of the XML package to get the data
library(XML)
## Get the data of the biggest ISO container companies from Wikipedia
##(table 3):
df=readHTMLTable(readLines("https://en.wikipedia.org/wiki/Intermodal_freight_transport"))[[3]][,1:2]
## Rename the second column
names(df)[2]="TEU capacity"
## The numbers are displayed with commas to separate thousands, so let's
## get rid of them:
df[,2]=as.numeric(gsub(",", "", as.character(df[,2])))

## Finally we can create a nice bar chart:
Bar5 <- gvisBarChart(df, options=list(
                    chartArea="{left:250,top:50,width:\"50%\",height:\"75%\"}",
                    legend="bottom", 
                    title="Top 20 container shipping companies in order of TEU capacity"))

plot(Bar5)

}