CSC121 - R Console
Friday January 19th
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> # Vectors
> 
> # One element vectors: the numbers we've been working with so far!
> 2
[1] 2
> 54
[1] 54
> # Notice the [1] beside the first (and only) element in the vector
> 
> # Let's make some multi-element vectors
> # Use the c(...) function
> c(3, 72)
[1]  3 72
> c(83, 4, 938)
[1]  83   4 938
> # Notice how the [1] is still there, beside the first element in each vector
> # Let's try a longer vector to see when there's more than just [1]
> c(234, 34234, 34534543, 453467567, 453534534, 5646456,345345345,35345345)
[1]       234     34234  34534543 453467567
[5] 453534534   5646456 345345345  35345345
> c(234, 34234, 34534543, 453467567, 453534534, 5646456,345345345,35345345)
[1]       234     34234
[3]  34534543 453467567
[5] 453534534   5646456
[7] 345345345  35345345
> c(234, 34234, 34534543, 453467567, 453534534, 5646456,345345345,35345345)
[1]       234     34234  34534543 453467567 453534534   5646456 345345345
[8]  35345345
> # In this case, since the vector spans more than one line, each line starts with [X] where X is the index of the element directly to the right of it
> 
> # Speaking of indexes, let's see how we can index a vector
> # Let's assign a vector to a variable
> v <- c(24, 5, 347, 97, 43)
> v
[1]  24   5 347  97  43
> v[1]
[1] 24
> v[2]
[1] 5
> # Now let's get a 'slice' of the vector
> v[1:3]
[1]  24   5 347
> # When we get a slice of the vector, we get back a NEW vector
> slice <- v[1:3]
> slice
[1]  24   5 347
> v
[1]  24   5 347  97  43
> length(v)
[1] 5
> v[length(v)]
[1] 43
> # length(v) evaluates to the length of the vector v, which is 5
> v[1:length(v)]
[1]  24   5 347  97  43
> 
> # We can work with values from vectors like we have before
> # Saving them to a variable
> a <- v[2]
> a
[1] 5
> # passing them as arguments to a function
> sqrt(v[4])
[1] 9.848858
> (v[3] + v[5]) / 2
[1] 195
> 
> # The type of the vector is the type of its elements
> typeof(v)
[1] "double"
> b <- c(1, as.integer(2.3), 5)
> typeof(b)
[1] "double"
> b
[1] 1 2 5
> typeof(b[2])
[1] "double"
>
> # typeof() only takes one argument
> typeof(b[2], b[1])
Error in typeof(b[2], b[1]) : unused argument (b[1])
> 
> # If everything in a vector is an integer, the type will be an integer
> g <- c(as.integer(2), as.integer(5))
> typeof(g)
[1] "integer"
>
> # You can change the type of the whole vector (we'll talk about vector manipulation next week)
> as.integer(c(2,5))
[1] 2 5
> typeof(as.integer(c(2,5)))
[1] "integer"
>
>
>
> #### Writing Distance Functions (can be found in distance_functions.R)
> source('~/distance_functions.R')
> 
> # Calling the function that doesn't use vectors
> # Notice we need two arguments for every point!
> DistanceWithoutVectors(-1, 2, 2, 6)
[1] 5
> source('~/distance_functions.R')
> 
> # With vectors, we can define a bunch of points as R vectors, and use our function to 
> # find the distance between them.
> A <- c(-1, 2)
> B <- c(2, 6)
> DistanceWithVectors(A, B)
[1] 5
>