instructR.R

# Here a set of instructions corresponding to each code lesson is made into a dataset codelist

ID=as.numeric() # id of code lesson
instruct=as.character() # instructions for code lesson
subhead=as.character()  # subheading for code lesson

i=1
ID[i]=i
subhead[i]="Simple R Expressions: Addition"
instruct[i]=paste('Try simple math','Type the command below','','1+1','',sep="\n")

i=i+1
ID[i]=i
subhead[i]="Simple R Expressions: Strings"
instruct[i]=paste('Type the following string','','"Hello, Shiny"','',sep="\n")

i=i+1
ID[i]=i
subhead[i]="Simple R Expressions: Multiplication"
instruct[i]=paste('Multiply 6*7','',sep="\n")

i=i+1
ID[i]=i
subhead[i]="Simple R Expressions: Logical"
instruct[i]=paste('Expressions can also return a logical value: TRUE or FALSE',
                  'Type the following expression which returns a logical value',
                  '','3 < 4',sep="\n")
          
i=i+1
ID[i]=i
subhead[i]="Simple R Expressions: Logical"
instruct[i]=paste('Another logical value, for equality use double == sign','','Type 2+2 == 5',sep="\n")

i=i+1
ID[i]=i
subhead[i]="Vectors with Sequence in R"
instruct[i]=paste('We want to get a vector from 1 to 20',
                  'We can use the seq function in R in the following way',
                  '',
                  '> seq(1,20)',
                  '',sep="\n")

i=i+1
ID[i]=i
subhead[i]="Vectors with Sequence in R"
instruct[i]=paste('We want to get a vector with 10 equally spaced values from 1 to 20',
                  'We can use the seq function in R in the following way',
                  '',
                  '> seq(1,20,length.out=10)',
                  '',sep="\n")

i=i+1
ID[i]=i
subhead[i]="Vectors with Sequence in R"
instruct[i]=paste('We want to get a vector from 1 to 20 that increments by 2',
                  'We can use the seq function in R in the following way',
                  '',
                  '> seq(1,20,by=2)',
                  '',sep="\n")

i=i+1
ID[i]=i
subhead[i]="Data Summary in R"
instruct[i]=paste('We want review what is in dataset mtcars',
                  'We can use the function head for this',
                  '',
                  '> head(mtcars)',
                  '',sep="\n")

i=i+1
ID[i]=i
subhead[i]="Data Summary in R"
instruct[i]=paste('We want review what is in dataset mtcars',
                  'We can use the function summary to get more information on the dataset',
                  '',
                  '> summary(mtcars)',
                  '',sep="\n")


i=i+1
ID[i]=i
subhead[i]="Plotting in R using ggplot2"
instruct[i]=paste('This part is based on code from Hadley Wickham\'s R book',
                  'ggplot2: Elegant Graphics for Data Analysis (http://ggplot2.org/book)',
                  'As in the book, we will work with a sample of 1000 records from diamonds dataset (store in data dsmall)',
                  'First, we view what is there in data',
                  '',
                  '> head(dsmall)',
                  '',sep="\n")

i=i+1
ID[i]=i
subhead[i]="Plotting in R using ggplot2: Scatter Plot"
instruct[i]=paste('We will create a scatter plot of price vs carat in mtcars data using ggplot2',
                  '',
                  '> p=qplot(carat,price,data=dsmall); print(p)',
                  '',sep="\n")

i=i+1
ID[i]=i
subhead[i]="Plotting in R using ggplot2: Scatter Plot"
instruct[i]=paste('We will color the scatter plot of price vs carat based on cut',
                  '',
                  '> p=qplot(carat,price,data=dsmall,color=cut); print(p)',
                  '',sep="\n")

i=i+1
ID[i]=i
subhead[i]="Plotting in R using ggplot2: Box Plot"
instruct[i]=paste('We will draw a box plot of price vs cut',
                  '',
                  '> p=qplot(cut,price,data=dsmall,geom="boxplot"); print(p)',
                  '',sep="\n")

i=i+1
ID[i]=i
subhead[i]="Plotting in R using ggplot2: Bar Plot"
instruct[i]=paste('We will draw a bar graph of cut',
                  '',
                  '> p=qplot(cut,data=dsmall,geom="bar"); print(p)',
                  '',sep="\n")

i=i+1
ID[i]=i
subhead[i]="Plotting in R using ggplot2: Bar Plot"
instruct[i]=paste('We will draw a bar graph of cut and fill each bar based on clarity',
                   '',
                   '> p=qplot(cut,data=dsmall,geom="bar",fill=clarity); print(p)',
                   '',sep="\n")



codelist=data.frame(cbind(ID,instruct,subhead))
codelist$instruct=as.character(codelist$instruct)
codelist$subhead=as.character(codelist$subhead)

server.R

library(shiny)
library(datasets)
library(ggplot2)
library(stringr)

# source the file that contains the instructions for each R code snippet
source("instructR.R")

# subset of diamonds dataset from ggplot2 package
# reference:
# ggplot2: Elegant Graphics for Data Analysis (http://ggplot2.org/book)
dsmall=diamonds[sample(nrow(diamonds),1000),]

shinyServer(function(input,output) {
  
  # Get subheading from codelist for a given value in code lesson input box
  output$subhead = reactiveText(function(){
    idx=input$ID
    codelist$subhead[idx]
  })
  
  # Get instructions on what code to type for a given value in code lesson input box
  output$instruct = reactivePrint(function(){
    idx=input$ID
    writeLines(codelist$instruct[idx])
  })
  
  # Run the code typed in the input text box
  
  # if the code text doesn't have plot substring run this piece to print out R output
  output$coderun = reactivePrint(function(){
      plotloc=str_locate(input$code,"plot")
      if(is.na(plotloc[1]) & (input$code != "")){
        eval(parse(text=input$code))
                        }
              })
  
  # if the code text has plot substring then run this piece to print out R plot
  output$codeplot = reactivePlot(function(){
    plotloc=str_locate(input$code,"plot")
    if(!(is.na(plotloc[1])) & (input$code != "")){
      eval(parse(text=input$code))
    }
  })
  
      })

ui.R

library(shiny)

shinyUI(pageWithSidebar(
  
  headerPanel("Attempt at Interactive R Learning"),
  
  sidebarPanel(
    
    helpText('TryR (http://tryr.codeschool.com) is a cool site set up to learn R. 
          I just wanted to play with Shiny to see if some basic form of that could be done in Shiny'),    
    br(),
    br(),
    numericInput("ID", "Code Lesson", 1), 
    submitButton("Update"),
    br(),
    helpText('To go to next code lesson, increment counter above and hit the update button. 
             A set of instructions for the lesson with appear on the right. You can directly go to
             any lesson by typing a lesson number above and hitting the update button. Since there 
             are 16 code lessons, the maximum number you can enter above is 16'),
    br(),
    helpText('In the right side main panel, you will notice NULL appearing. Please ignore it. 
             It is a result of my lack of R programming skills and I couldn\'t figure 
             out how to get rid of it')
    
    ),
  
  mainPanel(
    
    # subheading for the code lesson
    h3(textOutput("subhead")),
    
    # instructions for the code lesson
    verbatimTextOutput("instruct"),
    br(),
    
    # text box where R code can be typed
    textInput("code","Type code here and click update button on the left to run code"),
    
    # Output from R code typed if the code does not contain a plot substring
    verbatimTextOutput("coderun"),
    
    # Plot output from R code typed if the code contains a plot substring
    plotOutput("codeplot")
    
    )
  
  ))