R Programming

Data Structure

General Functions

.libPaths()                      # Show library paths
dir()                            # Show the directory
getwd()                          # Check working directory
setwd()                          # Change working directory
data()                           # Load built-in dataset
view()                           # View the entire dataset
tail()                           # Just show the last 6 rows
class()                          # Check the class of an R object
str()                            # Display internal structure of an R object
length()                         # Give length of a vector
dim()                            # View the number of rows and columns of a matrix or a data frame
names()                          # List names of variables in a data frame
set.seed()                       # Generate random number seed to make sure the results do not change.
ls()                             # list the variables in the workspace
rm()                             # remove the variable from workspace
rm(list = ls())                  # remove all the variables from the workspace
list.files()                     # List the filename under specific directory
.libPaths()                      # R installation site
help(package="")                 # Check the functions of R library
system.file(package=“dagdata”)   # Extract the location of package
colnames(installed.packages())   # list the installed packages

Coding Practice

• Variables = my_variable or myVariable
• Functions = RunThisStuffs() or run_this_stuffs()
• A function should not be longer than one screen
• Constants = CONSTANTS
• Use 4 spaces (and not tab) for indentations
• Always writing documentation above function definition
• Avoid using for loop, learn lapply and vector operations
• Never ever use hard-coded variables in functions
• ### ====== to divide function blocks
• ### ------ to divide parts in a function
• Name and style code consistently
• rm(list =ls()) and gc() to tidy up its memory
• Don’t save a session history
• Keep track of sessionInfo() in project folder
• Use version control

Variable Repacement

Common method to do the variable replacement in ggplot2:

• !!as.name()
• get()
• !!sym()
• .data[[]]

library(ggplot2)
data <- data.frame(
    x = c(1, 2, 3, 4),
    y = c(10, 20, 30, 40),
    group = c("A", "A", "B", "B")
)

color_var <- "group"
ggplot(data, aes(x = x, y = y, color = !!as.name(color_var))) +
    geom_point()

ggplot(data, aes(x = x, y = y, color = get(color_var))) +
    geom_point()


ggplot(data, aes(x = x, y = y, color = !!sym(color_var))) +
    geom_point()

ggplot(data, aes(x = x, y = y, color = .data[[color_var]])) +
    geom_point()

VSCode Setup

Remote Server Settings:

// Add these settings to the remote server
{
    "r.alwaysUseActiveTerminal": true,
    "r.bracketedPaste": true,
    "r.helpPanel.cacheIndexFiles": "Global",
    "r.plot.useHttpgd": true,
    "r.rmarkdown.chunkBackgroundColor": "",
    "r.rterm.option": [
        // "--r-binary=/home/zhonggr/miniforge3/envs/renv/bin/R",
        "--no-save",
        "--no-restore"
    ],
    "r.rpath.linux": "/home/zhonggr/miniforge3/envs/renv/bin/R",
    "r.rterm.linux": "/home/zhonggr/miniforge3/envs/renv/bin/radian"
}