Exercice2: build and learn

1. Let’s start: Copy, debug and run the first application (app1) presented today. 

2. Bin numbers: Change the application app1 to allow the user to enter the numbers of bins when plotting the histogram 

3. Server response: Change the application app1 to add some text as a response from server

4. Mean and Stdv: Change app1 so that
The user can enter different values for the mean and standard deviation
The mean and standard deviation are shown in the mainPanel
The user can enter a title for the histogram

5. Different displays: Change app1 so that the user can choose to do a histogram or a boxplot

6. Do it the way you want it: Just about anything can be made to look the way you want it. 
change the size of the sidebar (,width=3)
Change the aspect ratio of the graph plotOutput("plot", width = "500px", height = "500px")

7. Panel appears and disappears: 
An ugly feature of our app: the input field Number of bins only makes sense for the histogram, not for the boxplot, 
so it should not appear when we do a boxplot.
Hint: conditionalPanel

8. Predefined data sets
Let’s read files on the server files. For this purpose, first we need to save the data sets in the same folder as ui.R and server.R, say with dump
Then we can read the data in the server with
if(input$dataset=="Newcomb's Speed of Light") {
            source("newcomb.R")
            return(newcomb)
}

Your turn: Read the 3 data sets available on Moodle
 
9. Summary statistics:
In the text area we want a table of summary statistics.
The idea here is to use R syntax to create a character vector which has the lines of the HTML code.

10. Table presentations: These tables rarely look very good. To change their appearance we need to use cascading style files. The easiest way is to include that in the ui.R. 

11. Several panels: Often it is a good idea to have several panels to show different things. Say we want to separate the text from the graph.

12. Graph displays: Again there are items on the left that only make sense for the graphs, so they should only appear when the Graph panel is selected. Again conditionalPanel to the rescue!

13. Animation: When generating random data we might want to do this a number of times. Slowly, so one can watch the changes. 
On ui side use : 
sliderInput("k","Repeat!",min=1, max=10, value=0,step=1, 
                animate=animationOptions(interval = 500,playButton=“Go!")
         )
on server side use:
if(input$dataset=="Random") {
            for(i in 1:input$k) mu<-input$mu
            return(rnorm(input$n,input$mu,input$sig))
        }  

14. Use gglot2 library: Now let’s draw the graphs with ggplot2. For this purpose, you must add require(ggplot2) on server side and change the render plot function call for histogram and boxplot.