##### Lesson 11: Fran, the functionin' R-bot #####

# Setting the working directory 
setwd(“give the path to the folder“)
list.files()

# structure of a function #
functionname = function(inputs)
{
  instructions
  
  return(output)
}

# function to add two numbers #
add = function (a, b)
{
  y = a + b # instruction
  
  return (y) # the function "add" will take two numbers a and b and return y
}

# test the function #
add (10, 15)


# function for line equation #
line_eq = function (m, x, b)
{
  # m is the slope of the line 
  # b is the intercept of the line
  # x is the point on the x-axis
  
  y = m*x + b # equation for the line 
  
  return(y) 
}

# test the function #
line_eq(0.5, 5, 10)

# function for line equation + (x + y) #
two_tasks = function (m, x, b)
{
  # m is the slope of the line 
  # b is the intercept of the line
  # x is the point on the x-axis
  
  y = m*x + b # equation for the line 
  
  z = x + y
  
  return(c(y,z)) 
}

# test the function #
two_tasks(0.5, 5, 10)

# use on vectors #
x = c(1,2,3,4,5)
m = 0.5
b = 10

line_eq(m,x,b)

# function to analyze bike data # 
bike_analysis = function(bike_data,station_name)
{
  dum = which (bike_data$Start.Station.Name == station_name & bike_data$End.Station.Name == station_name)
  total_rides = length(dum)
  average_time = mean(bike_data$Trip.Duration[dum])/60 # in minutes 
  max_time = max(bike_data$Trip.Duration[dum])/60 # in minutes 
  min_time = min(bike_data$Trip.Duration[dum])/60 # in minutes
  
  output = c(total_rides,average_time,max_time,min_time)
  return(output)
}

# use the function to analyze Central Park South Loop #

# bike data # 
bike_data = read.csv("201703-citibike-tripdata.csv",header=T)

station_name = "Central Park S & 6 Ave"

bike_analysis(bike_data,station_name)