g language_charts_api

G-language Charts API

Overview

G-language Charts API is a RESTful web service for creating charts by accessing a simple URL. The charts are generated via R programming language through a CGI accessible with both GET and POST requests. Some examples are shown below:

The URL should be specified in the following format:

  http://rest.g-language.org/chart?cht=<chart_type>&chd=<chart_data>
  &chs=<chart_size>&…additional_parameters…

which is basically identical to the deprecated Google Charts API.

Making a Chart

A chart can be made by accessing a URL created manually.

Here are some instructions for creating a chart:

Select a chart type available, which can be seen from our Chart Gallery. The chart type is specified by the chd.
Prepare your chart data for drawing your chart. The data is specified by thechd parameter. Separate each series of values with "|" characters and each value with "," characters. Be careful as URL length is limited when accessing with a GET request, and if more length is needed try with a POST request.
Specify the chart size. The size is specified by the chs parameter, passed as number x number. For PDF, values are converted to inch assuming 72 dpi.
Pass additional parameters. The parameters available for each chart are listed in the parameter documentation page.
Build you URL string, according to the format above. The base URL for the API is http://rest.g-language.org/chart, followed with the parameters of your choice. Be sure to sanitize all HTML metacharacters in the URL when embedding into an HTML file.
Get your chart image, by accessing the URL with a GET request via web browser, or by embedding the image into HTML using tags. If the URL is too long, send a POST request instead.

Parameters

Here is a list of parameters available for styling your chart. Mandatory parameters have a star (*) by the name. More detailed information are provided below.

Parameter	Description	Chart Types
cht*	Chart Type	All charts
chd*	Chart Data	All charts
chs*	Chart Size	All charts
chfmt	Image Format	All charts
chtt	Chart Title	All charts
chxt	Axes Labels	All charts with X and Y axes
chco	Chart Colors	All charts
chls	Line Styles	Line chart
chlt	Line Types	Line chart
chdl	Chart Legend	All charts
chdlp	Legend Position	All charts

cht*

The type of chart to draw is specified by the "cht" parameter. A table of chart types and an example for each chart are shown in the Chart Gallery below. A quick list is as follows.

Chart Type	Value
Line Chart	lc
Line Chart (With x values)	lxy
Pie Chart	p
Box and Whisker Plot Chart	bw
Scatter Plot Chart	s
Bar Chart	b
Histogram Chart	h
Venn Diagram Chart	v

ex. cht=lxy

chd*

The data used for creating a chart is specified by the "chd" paramter. Data is to be passed as series of values, where series are separated with "|" characters and values are separated with "," characters. R format is supported otherwise.

  ex.
  chd=1,2,3,4,5|1,5,2,4,3
  chd=rnorm(50)

chs*

The size of the output chart is specified by the "chs" parameter. Data is to be passed in the format of widthxheight. When the output file format specified is a PDF, pixels are converted to inches, assuming the usage of 72 dpi.

 ex.
  chs=640x480

chfmt

The output image format of the chart is specified by the "chfmt" parameter. A list of available formats is as follows.

Default is png.

Format	Value
PNG	png
PDF	pdf
JPEG	jpeg
PostScript	postscript

  ex.
  chfmt=png

chtt

The title of a chart is specified by the "chtt" parameter. This may be any string value.

  ex.
  chtt=Sample Chart

chxt

The labels of the axes are specified by the "chxt" parameter. This may be any string value separated with a "," character. The option is valid for charts with x and y axes.

  ex.
  chxt=foo,bar

chco

The colors of the charts are specified by the "chco" parameter. There are two ways of passing values, which are either by using 6 digit hexadecimal values split by "," characters for each series, or the R way. The R native and RColorBrewer color libraries are available for use, and can be specified in the query. An easy way of using nice mat colors for the charts is by using the keyword "mat".

  ex.
  chco=ff0000,0000ff
  chco=mat
  chco=1,4

chls

The line style of the charts are specified by the "chls" parameter. Below is a list of types available.

Style	Value
Points	p
Lines	l
Points and Lines	b
"b" without Points	c
Overlapping Points and Lines	o
Vertical plots from x axis	h
Step from the left value	s
Step from the right value	S
Plot the axes only	n