CSC121 - R Console
Monday March 12th
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> getwd()
[1] "/Users/csc121/Desktop"
> studentData = read.table("students.txt")
> studentData
  V1        V2    V3   V4     V5  V6      V7
1 sn     lname fname year gender gpa program
2  1  Campbell   Jen    3      F 3.8      CS
3  2     Gries  Paul    2      M 2.7      CS
4  3 Dolderman   Dan    4      M 3.1     PSY
> # Don't forget to put header=TRUE
> studentData = read.table("students.txt", header=TRUE)
> studentData
  sn     lname fname year gender gpa program
1  1  Campbell   Jen    3      F 3.8      CS
2  2     Gries  Paul    2      M 2.7      CS
3  3 Dolderman   Dan    4      M 3.1     PSY
> View(studentData)
> nrow(studentData)
[1] 3
> ncol(studentData)
[1] 7
> dim(studentData)
[1] 3 7
> # We can change values in data frame
> studentData
  sn     lname fname year gender gpa program
1  1  Campbell   Jen    3      F 3.8      CS
2  2     Gries  Paul    2      M 2.7      CS
3  3 Dolderman   Dan    4      M 3.1     PSY
> studentData[2]
      lname
1  Campbell
2     Gries
3 Dolderman
> studentData[2,]
  sn lname fname year gender gpa program
2  2 Gries  Paul    2      M 2.7      CS
> studentData[2,]$gpa
[1] 2.7
> studentData[2,]$gpa <- 3.0
> studentData
  sn     lname fname year gender gpa program
1  1  Campbell   Jen    3      F 3.8      CS
2  2     Gries  Paul    2      M 3.0      CS
3  3 Dolderman   Dan    4      M 3.1     PSY
> # Data frame elements can be changed in place
> 
> # 'Querying' a data set to get a particular subset of data based on some condition
> # We can use the subset() function to extract data with certain conditions
> subset(studentData, gpa==3.8)
  sn    lname fname year gender gpa program
1  1 Campbell   Jen    3      F 3.8      CS
> subset(studentData, gpa>3.1)
  sn    lname fname year gender gpa program
1  1 Campbell   Jen    3      F 3.8      CS
> subset(studentData, gpa>=3.1)
  sn     lname fname year gender gpa program
1  1  Campbell   Jen    3      F 3.8      CS
3  3 Dolderman   Dan    4      M 3.1     PSY
> # Use '&' to combine conditions together
> subset(studentData, gpa>=3.1 & year==4)
  sn     lname fname year gender gpa program
3  3 Dolderman   Dan    4      M 3.1     PSY
> subset(studentData, gpa>=3.1 & year==6)
[1] sn      lname   fname   year    gender  gpa     program
<0 rows> (or 0-length row.names)
> studentData
  sn     lname fname year gender gpa program
1  1  Campbell   Jen    3      F 3.8      CS
2  2     Gries  Paul    2      M 3.0      CS
3  3 Dolderman   Dan    4      M 3.1     PSY
>
> # Column headers of the data frame are the 'names' of the data
> names(studentData)
[1] "sn"      "lname"   "fname"   "year"    "gender"  "gpa"    
[7] "program"
> names(studentData)[1]
[1] "sn"
> names(studentData)[1] <- "studentNum"
> studentData
  studentNum     lname fname year gender gpa program
1          1  Campbell   Jen    3      F 3.8      CS
2          2     Gries  Paul    2      M 3.0      CS
3          3 Dolderman   Dan    4      M 3.1     PSY
> subset(studentData, gpa>=3.1 & year==4)
  studentNum     lname fname year gender gpa program
3          3 Dolderman   Dan    4      M 3.1     PSY
> 
> 
>
> # Random Numbers
>
> runif(1,0,10)
[1] 3.707812
> runif(2,0,10)
[1] 7.332454 4.865090
> runif(1,0,10)
[1] 1.531535
> runif(1,0,10)
[1] 4.177907
> runif(1,0,10)
[1] 3.042981
> runif(1,0,10)
[1] 5.252659
> runif(1,0,10)
[1] 6.576456
> runif(1,0,10)
[1] 7.312626
> runif(1,0,10)
[1] 5.850115
> 
> plot(runif(500))