# 14-4-Exercise 2

### Function Definitions ###

# calculateOver12 - this will be applied to each row of the data frame
# The data frame row is referenced as 'x'
# Each element of the row is referenced as x[1], x[2], x[3] etc.

calculateOver12<-function(x)
{
  
  # Extract values from the row as numbers
  # The conversion is needed because the first column of the data frame
  # is vector of characters, so R assumes that all columns are characters
  totalAttendances<-as.numeric(x[3])
  under12Attendances<-as.numeric(x[6])
  
  # Calculate the number over 12 hours

  over12value<-totalAttendances-under12Attendances
  
  # Return the length-1 vector containing the difference
  return(over12value)
} # End of function calculateOver12

# getMinors  - this will be applied to each row of the data frame
# The data frame row is referenced as 'x'
# Each element of the row is referenced as x[1], x[2], x[3] etc.

getMinors<-function(x)
{
  # Check if the Size is Minor
  
  if (x[2]=="Minor")
  {
    # This returns a value only if the condition is TRUE
    return(x[1])
  }
  # If the condition is not TRUE then it will return a NULL
  
} # End of function getMinors

# getfast  - this will be applied to each row of the data frame
# The data frame row is referenced as 'x'
# Each element of the row is referenced as x[1], x[2], x[3] etc.

getFast<-function(x)
{
  # Check if the Over12 value is less than 1
  # Again, this needs to be converted as x[1] is a character vector
  if (as.numeric(x[8]<1))
  {
    # This returns a value only if the condition is TRUE
    return(x[1])
  }
  # If the condition is not TRUE then it will return a NULL
  
} # End of function getFast

# cleanUp - this will be applied to the result of getMinor and getFast
# The input list is referenced as 'l'
# The vector tempClean is returned

cleanUp<-function(l)
{
  # l is formatted as a list of lists
  # We need to unlist it to get it back to a vector tempClean
  
  tempClean<-unlist(l)
  
  # templClean is now formatted as a character vector with a header
  # We can convert it back to a pure vector of characters using as.vector
  
  tempClean<-as.vector(tempClean)
  
  # tempClean contains an element for every row in attendances
  # Select the unique elements using unique()
  
  tempClean<-unique(tempClean)
  
  # Return tempClean to main script
  
  return(tempClean)
} # End of cleanUp

### Main Script ###

# Load data file

attendances<-read.csv("SP14/ThreeMonthsMin.csv", header=TRUE)

# Calculate numbers waiting more than 12 hours
# apply(dataframe, 1=rows, function to be applied)

over12<-apply(attendances,1,calculateOver12)
over12 # Display the generated vector

# Bind newly-created column over12 onto the data frame with header 'Over12'
# It will have the right number of elements because one element was generated
# from each row of the original data frame

attendances<-cbind(attendances,Over12=over12)

# Get the names of all Minor units

minorUnits<-apply(attendances,1,getMinors)

# Clean up minorUnits

minorUnits<-cleanUp(minorUnits)

minorUnits # Display the generated vector of characters

# Display hospitals where no-one waited over 12 hours
# apply(dataframe, 1=rows, function to be applied)

fastHospitals<-apply(attendances,1,getFast)

# Clean up fastHospitals

fastHospitals<-cleanUp(fastHospitals)

fastHospitals # Display the generated vector of characters