CHEAT SHEET FOR R
By
Nanditha T (F17095)
Sanjana S (F17109)
Vivin Pearl Kishore (F17119) |
Util functions
getwd() |
gets the working directory |
setwd('c://file/path') |
sets the working directory |
ls() |
list all the variables |
rm(var_name) |
removes variable name |
str(variable name) |
displays the structure |
help.start() |
opens help |
install.packages("package_name") |
installs packages |
library("package_name") |
makes the content available to use |
detach("package_name") |
detaches the package |
history() |
displays history |
Data Structures
Vectors |
d=c(3,4,5) |
Arrays |
2D = array(1:24, dim = c(6,4)) |
Matrices |
mat = matrix(1:12, nrow=4, ncol=3) |
Lists |
list_data <- list("Red", "Green", c(21,32,11), TRUE, 5, 3) |
Dataframe |
df = data.frame(subjectID=1:5,gender=c("M","F","M","M","F"),score=c(8,3,6,5,5)) |
Vector
num = c(1,2,3,4,5,6) |
numeric vector |
chr = c("aaa","bbb") |
character vector |
log = c(TRUE,TRUE,FALSE) |
logical vector |
which.min(vec)/which.max(vec) |
position of the min/max value |
rep(1:5,times=3) |
Replicate elements of vector |
Arrays
1D = array(1:24) |
1-D array |
2D=array(1:24,dim=c(6,4)) |
2-D array |
3D=array(1:24,dim=c(4,3,2)) |
3-D array |
Matrix Functions
t(m) |
transpose |
m %*% n |
matrix multiplication |
solve(m,n) |
find x in m*x = n |
det(m) |
determinant |
m*n |
dot product |
rbind/cbind(mat1,mat2) |
row/column bind |
Data Frames
df = data.frame(subjectID=1:5,gender=c("M","F","M","M","F"),score=c(8,3,6,5,5)) |
Created data frames in R |
fw = read.csv(file.choose()) |
Importing data by choosing a file |
grass = read.csv('C:/path/sample.csv') |
Importing data by specifying paths |
view(df) |
opens editor |
rbind(a_data_frame, another_data_frame) |
Bind rows/ columns of frames |
merge(frame1, frame2, by = "x") |
Merge 2 data frames |
Descriptive Statistics
rowMeans(data[]) |
row mean |
rowSums(data[]) |
row sum |
colMeans(data[]) |
column mean |
colSums(data[]) |
column sum |
Data type Conversion
Use is.foo to test for data type foo. Returns TRUE or FALSE |
Use as.foo to explicitly convert it |
is.numeric(), is.character(), is.vector(), is.matrix(), is.data.frame()
as.numeric(), as.character(), as.vector(), as.matrix(), as.data.frame()
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Creating a Function
function_name <- function(arg_1, arg_2, ...) {
Function body
}
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Functions are followed by paranthesis
String functions
toString(x) |
produce a character string |
noquote(x) |
print character strings without quotes |
sprintf() |
returns a character vector containing a formatted combination of text and variable values |
cat() |
converts into strings and concatenates |
toupper() / tolower() |
converts text to uppercase/lowercase |
substr(x,first,last) |
extracts parts of a string |
strsplit(x, split, fixed = FALSE, perl = FALSE, useBytes = FALSE) |
split elements of a string into substrings |
paste(..., sep = " ", collapse = NULL) |
concatenate strings |
Factor functions
factor() |
it is used to encode a vector as a factor (the terms ‘category’ and ‘enumerated type’ are also used for factors) |
levels() |
it provides access to the levels attribute of a variable |
nlevels() |
Return the number of levels which its argument has. |
relevel() |
The levels of a factor are re-ordered so that the level specified by ref is first and the others are moved down |
unique() |
it returns a vector, data frame or array like x but with duplicate elements/rows removed. |
droplevels() |
The function droplevels is used to drop unused levels from a factor or, more commonly, from factors in a data frame |
cut() |
cut divides the range of x into intervals and codes the values in x according to which interval they fall |
Date Time functions
Sys.time() |
returns today's date |
date() |
returns current date and time |
as.POSIXlt() |
convert an object to one of the two classes used to represent date/times |
as.Date() |
convert character data to dates |
strptime() |
onverts character vectors to class "POSIXlt": its input x is first converted by as.character |
strftime() |
a wrapper for format.POSIXlt, and it and format.POSIXct first convert to class "POSIXlt" by calling as.POSIXlt |
Flow control functions
if(condition){ //execute when condition is true} |
if(condition){//execute when condition is true} else(){//execute when condition is false} |
if(condition 1) { // Executes when the condition 1 is true} else if( condition 2) { // Executes when the condition 2 is true. } else if( condition 3) { // Executes when the condition 3 is true} else { // executes when none of the above condition is true} |
ifelse(condition, x, y) |
switch(expression, case1, case2, case3....) |
Loop functions
while (condition){ Do something } |
for (variable in sequence){ Do something } |
apply(), lapply(), sapply() |
A loop statement allows us to execute a statement or group of statements multiple times based on the condition
File format functions
read.csv() |
To read the data |
read.table() |
To read the table contents |
read.xlsx2() |
To read data from excel sheet |
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Data summary functions
summary() |
returns descriptive statistics of data |
str() |
structure of the variable |
describe() |
determines the type of a single variable and prints a concise statistical summary |
class() |
a simple generic function mechanism which can be used for an object-oriented style of programming |
dim() |
Dimension |
head() |
Returns the first or last parts of a vector, matrix, table, data frame or function. |
names() |
Functions to get or set the names of an object. |
View() |
Invoke a spreadsheet-style data viewer on a matrix-like R object. |
subset() |
Return subsets of vectors, matrices or data frames which meet conditions. |
Visualization functions
par(mfrow=c(2,2)) |
create a matrix of nrows |
barplot() |
Relationship between a numerical and a categorical variable |
pie() |
piecharts |
mosaicplot() |
Plots a mosaic on the current graphics device |
hist() |
Histogram |
plot() |
simple scatter plots |
plot(density()) |
Density plots. non-parametric way to estimate the probability density function of a random variable |
pairs() |
A matrix of scatterplots is produced |
matplot() |
Plot the columns of one matrix against the columns of another. |
boxplot() |
Distribution |
qqnorm() |
produces quantile-quantile plot |
qplot() |
produces quantile-quantile plot |
ggplot(mydata1, aes(x = 1, fill = subject) ) + geom_bar() |
Intializes a ggplot object |
Probability Distributions
Central tendency and Dispersion
mean() |
find mean |
median() |
find median |
range() |
find range |
sd() |
find standard deviation |
var() |
find variance |
cor() |
find correlation |
Hypothesis Testing
t.test(data) |
1 sample t-test |
t.test(data1,data2) |
2 sample t-test |
t.test(pre,post,paired=TRUE) |
paired sample t-test |
wilcox.test(data) |
Wilcox test |
cor.test(data1,data2) |
Correlation test |
chisq.test(data) |
Chi square test |
shapiro.test(data) |
Shapiro test |
aov() |
ANOVA |
Algorithms - statistics
summary(lm(y ~ x1 + x2 + x3, data=mydata)) |
multiple regression |
summary(glm(y ~ x1 + x2 + x3, family="", data=mydata)) |
classification |
cluster = kmeans(data) |
clustering |
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