Learning R

learn_r.md

Learn R

course from GreatLearning

Introduction

types

• numeric (ex: 1, 2, 3.4 regardless of float and integer)
• character (string with one quote (') or two ("))
• logical (TRUE / T and FALSE / F, if combine in numeric will be T = 1, F = 0)
• complex (numeric with imaginary factor ex 13+6i)

get the type of var class(variable)

operators

• assignment = equal to operator variable <- value_to_be_assigned or value_to_assigned -> variable
• arithmetic + - * /
• relational > greater than, <, ==, !=
• logical & and, | or

vector linear homogenous data structure

• using combiner vec <- c(1,2,3,4,5)
• homogenous mean cannot be different type (ex: numeric and character
• if theres character than all variable converted into char, with order char > numeric > logical
• vec[2] get the second value of variable vec
• vec[1:3] get the value of vec from 1 to 3
• vec[c(1,3)] get the value of vec on index 1 and 3

list more like vector, but not homogenous (can have multiple type (num, char, logical, vector). l1 <- list(a, 'char', T) class(l1[[1]]) get the type of list index 1

matrix m1 <- matrix(c(1,2,3,4,5,6), nrow(2), ncol(3), byrow = T)

• nrow is to spread value in number of row
• ncol is to spread value in number of col
• byrow is to place the value by T: row first, F: col first
• to extract the value inside matrix m1[row, col] if row is empty than will extract for all row m1[, col] vice versa

array multi dimensional homogenous data structure (multi vector) example

vec1 <- c(1,2,3,4,5,6) vec2 <- c(7,8,9,10,11,12) #a1 <- array(c(vec1, vec2), dim=(row, col, numOfElementInArray) a1 <- array(c(vec1, vec2), dim=(2, 3, 2) extracting value from array, like getting from dim params a1[row, col, arrayIndex] read by taking

1. extract from array number index
2. get row from that array
3. get col from that array

factor and dataframe

• factor: to get the distinct value of a vector
• dataframe: 2 dimensional heterogenous data structure, simply like table in excel tblx <- data.frame(ColName1=c("v1","v2","v3"), ColName2=c("u1","u2","u3"))
• to get the value of col1 tblx$ColName1
• to view in table wise view(tblx), better to not do viewing on large dataset, will consume memory
• we can use tibble package for better viewing