# FC721 Introduction to R Programming
# Part1: Setting up R and RStudio
#-----------------------------------

# Check current directory
getwd()

# Set working directory
setwd("/Users/ktrn/BOSTON UNIVERSITY Dropbox/Katia Bulekova/Classes/FC721")

# Install packages
install.packages("tidyverse")
# Alternatively you can install R packages using RStudio GUI
# Tools -> Install Packages
# Type in the package name and click Install

# Load packages
library(tidyverse)
# Note 1:  you have to use quotes with install.packages() but not with library()
# Note 2:  you need to install a package only once, but you need to load it every time you start a new R session
# Note 3:  load the packages you need at the beginning of your script

#-----------------------------------
# Basic R data types
#-----------------------------------

# Numeric
x <- 5
class(x)

# Character
y <- "Hello, World!"
class(y)

# Values of the same data types can be combined in a vector:
z <- c(1, 21, 35, 74, 5)
class(z)


# systolic blood pressure values
SBP <- c(96, 110, 100, 125, 90 )

# diastolic blood pressure
DBP <- c(55, 70, 68, 100, 50)

# calculate MAP (mean arterial pressure)
MAP <- SBP/3 + 2*DBP/3
MAP

# vector functions:
#               max(x),   min(x),  sum(x),     prod(),
#               mean(x),  sd(),    median(x),  range(x)
#               sort(x),  rank(x),    order(x)
#               cumsum(), cumprod(x), cummin(x), cummax(x)
#               var(x)                            - simple variance
#               cor(x,y)                          - correlation between x and y
#               duplicated(x), unique(x)
#               summary()

# Vector slicing:
MAP[2]         # returns second element 
MAP[2:4]       # returns second through 4th elements inclusive
MAP[c(1,3,5)]  # returns 1st, 3rd and 5th elements

#-----------------------------------
# Getting R help
#-----------------------------------

# If you need help with a specific function, you can use the help() function:
help(mean)

# You can also use the question mark symbol ? to get help:
?mean

# If you are looking for a topic but do not know the function name, you can use double question marks ??
??"standard deviation"