Error Bar Charts in R
Chapter 4 of DSUR - Graphing Means - pp 145-154
Discovering Statitics Using R

1. The textbook example file ChickFlick.dat is delimited, not comma separated values.

   > chickFlick <- read.delim("C:/R/AndyField/ChickFlick.dat", header=T)
   
   > chickFlick
      
      gender                 film arousal
   1    Male Bridget Jones' Diary      22
   2    Male Bridget Jones' Diary      13
   3    Male Bridget Jones' Diary      16
    ...
   
   38 Female              Memento      31
   39 Female              Memento      22
   40 Female              Memento      14
   

2. Why do we do the attach() command?

   > gender
   Error: object 'gender' not found    <------- This is WHY...
      
   > attach(chickFlick)                                 ---
       
   > gender
    [1] Male   Male   Male   Male   Male   Male   Male   Male   Male   Male  Male   Male   Male   Male  
   [15] Male   Male   Male   Male   Male   Male   Female Female Female Female Female Female Female Female
   [29] Female Female Female Female Female Female Female Female Female Female Female Female
   Levels: Female Male
       
   > names(chickFlick)
   [1] "gender"  "film"    "arousal"
   

3. Need to use the ggplot() function from the ggplot2 package.
   Is the package installed? Need to do install.package()
   Is it installed already, but not loaded? library()

   > bar <- ggplot(chickFlick, aes(film, arousal))
   Error: could not find function "ggplot"
   
     Note: install.package("ggplot2") was NOT needed.  It was installed
                                                             3 days ago.   
           library("ggplot2") command was all that was needed.
           library(ggplot2) works too.
   
           See page 121 of the DSUR book.
   
   > library("ggplot2", lib.loc="C:/Users/Mark/Documents/R/win-library/3.0")
   
     Note:   library("ggplot2") is ENOUGH.
             The above syntax is what you get if you go to the Packages
                 panel and check the unchecked checkbox for package ggplot2.
      
   > bar <- ggplot(chickFlick, aes(film, arousal))
   

4. Using the ggplot graph and outputting it as a bar graph.

   > bar + stat_summary(fun.y = mean, geom = "bar", fill = "White", colour = "Black") 
     + stat_summary(fun.data = mean_cl_normal, geom = "pointrange")
      
   Error : Hmisc package required for this functionality.  Please install and try again.
      
   > install.packages("Hmisc")
   Installing package into C:/Users/Mark/Documents/R/win-library/3.0 (as lib is unspecified)
        also installing the dependency Formula
      
   package Formula successfully unpacked and MD5 sums checked
   package Hmisc successfully unpacked and MD5 sums checked
   

5. Here is the geom = "pointrange" contrasted with geom = "errorbar" output.

   > bar + stat_summary(fun.y = mean, geom = "bar", fill = "White", colour = "Black") 
     + stat_summary(fun.data = mean_cl_normal, geom = "pointrange") 
     + labs(x = "Movie", y = "Mean Excitement from watching sample of film")
      
   > bar + stat_summary(fun.y = mean, geom = "bar", fill = "Yellow", colour = "Black") 
     + stat_summary(fun.data = mean_cl_normal, geom = "errorbar") 
     + labs(x = "Movie", y = "Mean Excitement from watching sample of film")
   

   
   geom = "pointrange" is white graph on the left... ------------ ...geom = "errorbar" is yellow graph on the right...

6. Bar charts for several independent variables via fill=gender for DSUR example file (still stored in chickFlick dataframe).

   > bar2 <- ggplot(chickFlick, aes(film, arousal, fill=gender))
      
   > bar2 + stat_summary(fun.y = mean, geom = "bar")
   
             The above command works, but the FEMALE bars are hidden
                 by the MALE bars.
      
   > bar2 + stat_summary(fun.y = mean, geom = "bar" position="dodge")
   Error: unexpected symbol in "bar2 + stat_summary(fun.y = mean, geom = "bar" position"
   
               Oops, need a comma between each stat_summary() argument! , , ,
   
   > bar2 + stat_summary(fun.y = mean, geom = "bar", position="dodge")
   
               This works fine and the bars are side by side...
     
   > bar2 + stat_summary(fun.y = mean, geom = "bar", position="dodge") 
          + stat_summary(fun.data = mean_cl_normal, geom = "errorbar", 
            position = position_dodge(width = 0.90), width = 0.2) 
          + labs(x = "Film", y = "Mean Arousal", fill = "Gender")
   

   

7. Here is the same bar chart, but with width = 0.4 and more descriptive x axis and y axis labels.

   > bar2 + stat_summary(fun.y = mean, geom = "bar", position="dodge") + 
            stat_summary(fun.data = mean_cl_normal, geom = "errorbar", 
            position = position_dodge(width = 0.90), width = 0.4) 
          + labs(x = "Film Title", y = "Mean Arousal from watching selection", fill = "Gender")