Utility Functions
getwd() |
Find the working dir. |
setwd("C:/file/path") |
Set the working dir. |
ls() |
List variables |
rm(object) |
Delete object |
str(object) |
Displays internal structure of R object |
help.start() |
Launch help console |
install.packages("package_name") |
Install package |
library(package_name) |
Load package |
detach(package:package_name) |
Remove package |
scan() |
Read data values |
Lists
list(x=1:5, y=c('a', 'b')) |
Create list |
is.list()
Check if the arg is a list |
as.list()
Force the arg to list |
lapply(list_name, function)
Apply function over a list and return as list |
sapply(list_name, function)
Return as suitable data structure(vector) |
Strings
c("String1","String2") |
Create a string vector |
toString(x) |
Convert to string |
noqutoe(string) |
Print string w/o quote |
sprintf() |
Print text & var values |
cat() |
Concatenate & print |
toupper(string) |
Convert to uppercase |
tolower(string) |
Convert to lowercase |
substr(string,n,m) |
Extract substrings in a string from n to m |
strsplit(string," ") |
Split elements of string |
paste(c("a","b"),"c")
Concatenate vectors |
paste0(c("a","b"),"c")
Concat w/o separator |
Probability Distributions
rbinom(n, size, prob) |
Binomial |
rpois(n, lambda) |
Poisson |
runif(n, min=0, max=1) |
Uniform |
rnorm(n, mean=0, sd=1) |
Normal |
rexp(n, rate=1) |
Exponential |
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Vectors
c(2, 4, 6) |
Numeric vector |
c("one","two","thr") |
Character vector |
c(TRUE,FALSE) |
Logical vector |
rep(1:2,times=3) |
Repeat a vector |
rep(1:2,each=3) |
Repeat the elements |
which.min()
Index of the min |
which.max()
Index of the max |
Data Frames
data.frame(x=1:2,
y=c('a', 'b')) |
Create data frame |
View(df_name) |
See full dataframe |
head(df_name) |
See first 6 rows |
tail(df_name) |
See last 6 rows |
df_name[cond, ] |
Row filter |
df_name[c("column")] |
Column filter |
df_name[cond1, ][ ,cond2]
Row and Column filter |
Functions
function_name <- function(var){
Do something
return(new_variable)}
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args(function_name) - Arguments of func
body(function_name) - Body of func
Flow Control
If Statement -
if (condition){
Do something
} else {
Do something different}
-------------------------------
Ifelse Statement -
ifelse(condition, Do something, Do something different)
-------------------------------
Switch Statement -
switch("beta","alpha=1,beta=2,gamma=3,4)
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Loops
For Loop -
for (var in sequence){Do something} |
While Loop -
while (condition){ Do something} |
Visualizations
barplot() |
plot() |
qqnorm() |
pie() |
plot(density()) |
qplot() |
mosaicplot() |
pairs() |
boxplot() |
hist() |
matplot() |
ggplot() |
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Arrays
array(1:24, dim=c(4,3,2), dimnames=......)
Create array with 4 rows, 3 cols and 2 groups |
Matrices
m1 <- matrix(1:12, now=4, ncol=3, dimnames=....)
Create a matrix with 4 rows and 3 columns |
t(m) |
Transpose of matrix |
rbind(m1,m2)
Combine by row |
cbind(m1,m2)
Combine by column |
The following applies to arrays also: |
dimnames(m) |
dim(m) |
colnames(m) |
rownames(m) |
nrow(m) |
ncol(m) |
Descriptive Statistics
summary(object) |
Summary of object |
class(object) |
Find class of an R object |
length(object) |
Get length of an object |
quantile(x) |
Find quantiles |
rowMeans(x)/
colMeans(x) |
rowSums(x)/
colSums(x) |
table(x) |
Build a contingency table |
describe(object) |
Description of object |
subset(x,cond) |
Create subsets |
Hypothesis Testing
t.test(data, mu=3)
One sample two-sided t-test |
t.test(data, mu=3, alternative='greater')
One sample one-sided t-test |
t.test(data1, data2, mu=0.5)
Two sample two-sided t-test |
t.test(data1, data2, mu=0.5, alternative='less')
Two sample one-sided t-test |
t.test(post_data, pre_data, paired=TRUE)
Paired test |
wilcox.test(data, mu=8, alt='less')
Wilcoxen test |
cor.test(data1, data2)
Correlation test |
chisq.test(data)
Chi-square test |
ks.test(data1, data2)
If both are frm same distn |
shapiro.test(data)
Normality test |
aov(data1~ data2)
ANOVA |
lm(data1~ data2)
Regression |
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