CSC121 - R Console
Friday March 9th
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> # Max and min functions
> max(c(4,3,1,7,2))
[1] 7
> min(c(4,3,1,7,2))
[1] 1
>
> # DATA FRAMES
> # Reading into a data frame from a text file online
> heights_and_weights <-
+     read.table ("http://www.cs.utoronto.ca/~radford/csc121/data7",
+                 header=TRUE)
> heights_and_weights
  name height weight
1 Fred     62    144
2 Mary     60    131
3  Joe     71    182
> 
> View(heights_and_weights)
> 
> # Checking NAs: use is.na()
> is.na(NA)
[1] TRUE
> a <- c(NA, 4, NA, 6, NA, NA)
> is.na(a)
[1]  TRUE FALSE  TRUE FALSE  TRUE  TRUE
> 
> # Let's read in our students data
> getwd()
[1] "/Users/csc121"
> setwd("/Users/csc121/Desktop")
> getwd()
[1] "/Users/csc121/Desktop"
> studentData <- read.table("students.txt", header=TRUE)
Warning message:
In read.table("students.txt", header = TRUE) :
  incomplete final line found by readTableHeader on 'students.txt'
> # ^ Don't forget to add a new line to the end of text file with data
> 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
> # Notice how column names and the data beneath them line up correctly
> View(studentData)
> studentData$fname
[1] Jen  Paul Dan 
Levels: Dan Jen Paul
> # We'll talk about the 'Levels' next week
>
> # We can access different rows, columns, and specific elements of the data frame
> studentData$gpa
[1] 3.8 2.7 3.1
> studentData[1,]
  sn    lname fname year gender gpa program
1  1 Campbell   Jen    3      F 3.8      CS
> studentData[1:2,]
  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
> studentData[c(1,3),]
  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
>