Completed work on Section 2: Data

Section_2_Data/section2.R

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+# Ex. 2.1
+#  You can read in a sequence of space-separated values with scan
+#  miles <- scan()
+miles <- c(65311, 65624, 65908, 66219, 66499, 66821, 67145, 67447)
+x <- diff(miles)
+
+max(x)
+# [1] 324
+
+mean(x)
+# [1] 305.1429
+
+min(x)
+# [1] 280
+
+# Ex. 2.2
+commutes <- c(17, 16, 20, 24, 22, 15, 21, 15, 17, 22)
+
+max(commutes)
+# [1] 24
+
+mean(commutes)
+# [1] 18.9
+
+min(commutes)
+# [1] 15
+
+# Oops, the 24 was a mistake
+# It should have been 18
+commutes[commutes==24]=18
+commutes
+# [1] 17 16 20 18 22 15 21 15 17 22
+
+mean(commutes)
+# [1] 18.3
+
+sum(commutes >= 20)
+# [1] 4
+
+n <- length(commutes)
+l <- length(which(commutes<17))
+l/n
+# [1] 0.3
+
+
+# Ex. 2.3
+bill <- c(46, 33, 39, 37, 46, 30, 48, 32, 49, 35, 30, 48)
+
+sum(bill)
+# [1] 473
+
+min(bill)
+# [1] 30
+
+max(bill)
+# [1] 49
+
+length(which(bill<40))
+# [1] 7
+
+n <- length(bill)
+l <- length(which(bill<40))
+l/n
+# [1] 0.5833333
+
+
+# Ex. 2.4
+prices <- c(9000, 9500, 9400, 9400, 10000, 9500, 10300, 10200)
+
+# The average price is much higher than 9500 USD
+mean(prices)
+# [1] 9662.5
+
+min(prices)
+# [1] 9000
+
+max(prices)
+# [1] 10300
+
+
+# Ex. 2.5
+# Given:
+#   x = c(1,3,5,7,9)
+#   y = c(2,3,5,7,11,13)
+#
+# 1. x+1
+# 2. y*2
+# ... operations are mapped to each vector element
+# 3. length(x) and length(y)
+# ... returns the respective vector lengths
+# 4. x + y
+# .... returns warning that the vectors are of different lengths
+# 5. sum(x>5) and sum(x[x>5])
+# ... first will return the number of elements > 5
+# ... latter will return sum of elements > 5
+# 6. sum(x>5 | x< 3) # read | as 'or', & and 'and'
+# ... number of elements > 5 and < 3
+# 7. y[3]
+# ... 3rd element of y
+# 8. y[-3]
+# ... all elements of y except 3rd one
+# 9. y[x] (What is NA?)
+# ... returns elements of y with indices as listed
+#     as the elements of x, but the indices beyond
+#     the range of y are NA (or null)
+# 10. y[y>=7]
+# ... returns all elements of y >= 7
+
+
+# Ex. 2.6
+x <- c(1, 8, 2, 6, 3, 8, 5, 5, 5, 5)
+
+# 1.
+sum(x)/10
+# [1] 4.8
+
+# 2.
+log(x, base=10)
+# [1] 0.0000000 0.9030900 0.3010300 0.7781513 0.4771213 0.9030900 0.6989700
+# [8] 0.6989700 0.6989700 0.6989700
+# ... log10(x) also works
+
+# 3.
+(x-4.4)/2.875
+# [1] -1.1826087  1.2521739 -0.8347826  0.5565217 -0.4869565  1.2521739
+# [7]  0.2086957  0.2086957  0.2086957  0.2086957
+
+# 4.
+diff(range(x))
+# [1] 7
+