Add installation on R (#90)

Author: kozo2

README.md

@@ -14,7 +14,7 @@ A Dash component library for creating interactive and customizable networks in P
 
 ## Getting Started
 
-### Prerequisites
+### Prerequisites (Python)
 
 Make sure that dash and its dependent libraries are correctly installed:
 ```commandline
@@ -23,8 +23,13 @@ pip install dash dash-html-components
 
 If you want to install the latest versions, check out the [Dash docs on installation](https://dash.plotly.com/installation).
 
+### Prerequisites (R)
 
-### Usage
+```R
+install.packages(c("devtools", "dash"))
+```
+
+### Usage (Python)
 
 Install the library using pip:
 
@@ -58,6 +63,43 @@ if __name__ == '__main__':
 
 ![basic-usage](https://raw.githubusercontent.com/plotly/dash-cytoscape/master/demos/images/basic-usage.gif)
 
+### Usage (R)
+
+Install the library using devtools:
+
+```
+devtools::install_github("plotly/dash-cytoscape")
+```
+
+Create the following example inside an `app.R` file:
+
+```R
+library(dash)
+library(dashHtmlComponents)
+library(dashCytoscape)
+
+app <- Dash$new()
+
+app$layout(
+  htmlDiv(
+    list(
+      cytoCytoscape(
+        id = 'cytoscape-two-nodes',
+        layout = list('name' = 'preset'),
+        style = list('width' = '100%', 'height' = '400px'),
+        elements = list(
+          list('data' = list('id' = 'one', 'label' = 'Node 1'), 'position' = list('x' = 75, 'y' = 75)),
+          list('data' = list('id' = 'two', 'label' = 'Node 2'), 'position' = list('x' = 200, 'y' = 200)),
+          list('data' = list('source' = 'one', 'target' = 'two'))
+        )
+      )
+    )
+  )
+)
+
+app$run_server()
+```
+
 ### External layouts
 
 You can also add external layouts. Use the `cyto.load_extra_layouts()` function to get started: