Data Frame

source “K-MOOC 오세종 교수님의 [R 데이터 분석 입문] 강좌의 3-2. data frame 중 (http://www.kmooc.kr/courses/course-v1:DKUK+DKUK0003+2020_T3)”

data frame

Create data frame

city<- c("Seoul", "Tokyo", "Washington")
rank<- c(1, 3, 2)
city.info<- data.frame(city, rank)

We usually call data from file

dataset

iris: dataset used in R

Extract column data from data.frame

is.data.frame(iris) #Is iris data frame?
[1] TURE

• Can be used like matrix

iris[,"Species"] # the result is a horizontal (1D) vector
iris["Species"] # column direction: data frame of 150 row and 1 column
iris$Species # same result with iris[, "Species"]. Cannot be used for matrix, needed to converted

Commands for both data frame and matrix

iris[, c(1:2)] # 1st, 2nd columns. data frame
iris[, c(1, 3, 5)] # combine col 1, 3, 5  data frame
iris[, c("Sepal.Length", "Species")] # bring 2 columns Sepal.Length and Species
iris[1:50,] # cut row 1 to row 50
iris[1:50, c(1,3)] # cut row 1 to row 50, and cut column 1 and column 3

Assignment

1. Create data frame df

>df
  id   name  score
1 10  John      95
2 20   Tom      46
3 30  Paul      98
4 40  Jane      74
5 50 Grace      85

1. Compare df$score, df[,3], df[, ‘score’]

2. Print values of column id and score

3. Print values of row 2, row 3

4. Print the value of row 2, column 3

id<- c(10,20,30,40,50)
name<- c("John", "Tom", "Paul", "Jane", "Grace")
score<- c(95, 46, 98, 74, 85)

df<- data.frame(id, name, score)
df
df$score #same results for df$score, df[,3], and df[,'score']
df[,3]
df[,'score']
df[, c("id", "score")]
df[2:3,]
df[2, 3]

back next Index

Comments

Post comment

Loading...