R tutorials

• Should you write code just to get your work done?
• Do you need to care for reusability?
• Do you write user friendly code as well as programmer friendly code?

All styles have same results, one is better other is best of all

• Style 1

a <- 10
b <- 20
c <- (10+20)/2
c

[1] 15

All styles have same results, one is better other is best of all

• Style 2

variable_number_1 <- 10 
variable_number_2 <- 20
third_variable <- mean(c(variable_number_1,variable_number_2))
print(third_variable)

[1] 15

All styles have same results, one is better other is best of all

• Style 3

# Add comments
# Indent if it improves readability
var1 <- 10  # First variable
var2 <- 20  # Second variable
# Calculate average value using standard mean() function
average_value <- mean(c(var1,var2)) 
# Display the average value properly
cat('Mean value is : ',average_value) 

Mean value is :  15

# Install a package everytime you run a script
install.packages("nnet")
# Import your package
library(nnet)

# Writing a robust code - a nice way to check & install a package
load_pkgs <- c("e1071","caret")
# Perform a for loop for each item in pkg list
for (i in load_pkgs) 
{
    if(! (i %in% installed.packages())) # If package is not installed
        install.packages(i) # Install the package
    do.call('library',as.list(i)) # Load the library if already installed
}

# To know the version of R which you are using
version   
# Automatically update your r version with the package installr
library(installr)
# Use updateR() function to update R
updateR()

numbers <- 1:10000000
system.time({ # R is case sensitive ('System' is not equals to 'system')
  total <- 0
  for(i in numbers) # Iterative approach
    total <- total + i
  cat("Sum is : ",total,"\n")
})

Sum is :  5e+13 

   user  system elapsed 
   0.35    0.00    0.35 

# Try writing efficient programs (Save time)
numbers <- 1:10000000
system.time({ 
  total <- 0
  total <- sum(c(numbers))  # Vectorized code
  cat("Sum is : ",total,"\n")
})

Sum is :  5e+13 

   user  system elapsed 
   0.13    0.00    0.12 

# Ctrl + Shift + C  # Comment selected lines
# Ctrl + Shift + R  # Insert section
# Ctrl + L  # Clear console
rm(list=ls())   # Clear all workspace variables
# Use an IDE such as RStudio
cat('\f') # To clear your console

# Press [`Alt` + `-`] to put <- or `assignment operator` in RStudio

• Official website for R https://www.r-project.org/
• Official R studio website https://www.rstudio.com/
• GitHub repositories https://depthgr8.github.io/