R Data Structures

# create vectors of data for three medical patients
President_name <- c("Omar Jeanmary", "Rose Lee", " Alicia Malcolm")
salary <- c( 30000.00, 40000.00, 5000.00)
Application_status <- c(FALSE, FALSE, TRUE)

# access the second element in body temperature vector
salary[2]

## [1] 40000

# include items in the range 2 to 3
salary[2:3]

## [1] 40000  5000

# exclude item 2 using the minus sign
salary[-2]

## [1] 30000  5000

# add ordered factor
Government <- factor(c("SEVERE", "MILD", "MODERATE"),
                   levels = c("MILD", "MODERATE", "SEVERE"),
                   ordered = TRUE)
Government

## [1] SEVERE   MILD     MODERATE
## Levels: MILD < MODERATE < SEVERE

# check for symptoms greater than moderate
Government > "MODERATE"

## [1]  TRUE FALSE FALSE

President_name[1]

## [1] "Omar Jeanmary"

salary[1]

## [1] 30000

Application_status[1]

## [1] FALSE

Government[1]

## [1] SEVERE
## Levels: MILD < MODERATE < SEVERE

# create list for a president
subject1 <- list(fullname = President_name[1], 
                 salary= salary[1],
                 Application_status = Application_status[1],
                 Government = Government[1])
subject1

## $fullname
## [1] "Omar Jeanmary"
## 
## $salary
## [1] 30000
## 
## $Application_status
## [1] FALSE
## 
## $Government
## [1] SEVERE
## Levels: MILD < MODERATE < SEVERE

pt_data <- data.frame(President_name, salary, Application_status, Government = FALSE)
pt_data

##    President_name salary Application_status Government
## 1   Omar Jeanmary  30000              FALSE      FALSE
## 2        Rose Lee  40000              FALSE      FALSE
## 3  Alicia Malcolm   5000               TRUE      FALSE

# get a single column
pt_data$President_name

## [1] "Omar Jeanmary"   "Rose Lee"        " Alicia Malcolm"

# get several columns by specifying a vector of names
pt_data[c("salary", "Application_status")]

##   salary Application_status
## 1  30000              FALSE
## 2  40000              FALSE
## 3   5000               TRUE

# accessing by row and column
pt_data[2, 2]

## [1] 40000

# accessing several rows and several columns using vectors
pt_data[c(1, 2), c(2, 3)]

##   salary Application_status
## 1  30000              FALSE
## 2  40000              FALSE

# create a 2x2 matrix
m1 <- matrix(c(1, 2, 3, 4), nrow = 2)
m1

##      [,1] [,2]
## [1,]    1    3
## [2,]    2    4

# equivalent to the above
m1 <- matrix(c(1, 2, 3, 4), ncol = 2)
m1

##      [,1] [,2]
## [1,]    1    3
## [2,]    2    4

# create a 2x3 matrix
m2 <- matrix(c(1, 2, 3, 4, 5, 6), nrow = 2)
m2

##      [,1] [,2] [,3]
## [1,]    1    3    5
## [2,]    2    4    6

m4<-matrix(c(3,3,7,9,11,10),ncol = 2)
m4

##      [,1] [,2]
## [1,]    3    9
## [2,]    3   11
## [3,]    7   10

#let us extract the first  row
m4[1,]

## [1] 3 9

m4[,2]

## [1]  9 11 10