I have this piece of code that calculates the vector "week1" (predefined in the exercise), based on the number of times a value is repeated in that column. I would need to create a function that does the same for the other 6 columns (from 2 to 7), using the function apply, but I struggle a bit with functions yet.
This is the piece of code:
matrix <- matrix(1, 16, 7)
week1 <- matrix[,1]
times <- tabulate(week1, 4)
vectorW1 <- c(1/times[1], 1-1/times[1], 1/times[2], 1-1/times[2],
1/times[3], 1-1/times[3],1/times[4], 1-1/times[4])
Thank you all in advance for your help!
I've no idea what this code is trying to do, nor what the target function is attempting to do.
First, let us make it into a function
mat_to_weights <- function(data) {
stopifnot(inherits(data, "matrix"))
result <- matrix(NA, nrow = 8, ncol = ncol(data))
for (col in seq_len(ncol(data))) {
week <- data[, col]
week
times <- tabulate(week, 4)
times
vector <-
c(
1 / times[1],
1 - 1 / times[1],
1 / times[2],
1 - 1 / times[2],
1 / times[3],
1 - 1 / times[3],
1 / times[4],
1 - 1 / times[4]
)
result[,col] <- vector
}
result
}
mat_to_weights(data = matrix)
> mat_to_weights(data = matrix)
[,1] [,2] [,3] [,4] [,5] [,6] [,7]
[1,] 0.0625 0.0625 0.0625 0.0625 0.0625 0.0625 0.0625
[2,] 0.9375 0.9375 0.9375 0.9375 0.9375 0.9375 0.9375
[3,] Inf Inf Inf Inf Inf Inf Inf
[4,] -Inf -Inf -Inf -Inf -Inf -Inf -Inf
[5,] Inf Inf Inf Inf Inf Inf Inf
[6,] -Inf -Inf -Inf -Inf -Inf -Inf -Inf
[7,] Inf Inf Inf Inf Inf Inf Inf
[8,] -Inf -Inf -Inf -Inf -Inf -Inf -Inf
Next, instead of a matrix with 1s, let us try to use dummy matrix from pracma::magic(n).
> mat_to_weights(data = pracma::magic(1))
[,1]
[1,] 1
[2,] 0
[3,] Inf
[4,] -Inf
[5,] Inf
[6,] -Inf
[7,] Inf
[8,] -Inf
> mat_to_weights(data = pracma::magic(2))
[,1] [,2]
[1,] 1 Inf
[2,] 0 -Inf
[3,] Inf 1
[4,] -Inf 0
[5,] Inf 1
[6,] -Inf 0
[7,] 1 Inf
[8,] 0 -Inf
Warning message:
In pracma::magic(2) : There is no magic square of order 2.
> mat_to_weights(data = pracma::magic(3))
[,1] [,2] [,3]
[1,] Inf 1 Inf
[2,] -Inf 0 -Inf
[3,] Inf Inf 1
[4,] -Inf -Inf 0
[5,] 1 Inf Inf
[6,] 0 -Inf -Inf
[7,] 1 Inf Inf
[8,] 0 -Inf -Inf
> mat_to_weights(data = pracma::magic(4))
[,1] [,2] [,3] [,4]
[1,] Inf Inf Inf 1
[2,] -Inf -Inf -Inf 0
[3,] Inf 1 Inf Inf
[4,] -Inf 0 -Inf -Inf
[5,] Inf Inf 1 Inf
[6,] -Inf -Inf 0 -Inf
[7,] 1 Inf Inf Inf
[8,] 0 -Inf -Inf -Inf
> mat_to_weights(data = pracma::magic(5))
[,1] [,2] [,3] [,4] [,5]
[1,] Inf Inf 1 Inf Inf
[2,] -Inf -Inf 0 -Inf -Inf
[3,] Inf Inf Inf 1 Inf
[4,] -Inf -Inf -Inf 0 -Inf
[5,] Inf Inf Inf Inf 1
[6,] -Inf -Inf -Inf -Inf 0
[7,] 1 Inf Inf Inf Inf
[8,] 0 -Inf -Inf -Inf -Inf
Again, not clear this is supposed to do, but the function works.
Let us rewrite it with apply in mind.
mat_to_weights <- function(data) {
stopifnot(inherits(data, "matrix"))
result <- matrix(NA, nrow = 8, ncol = ncol(data))
apply(data, 2, function(week) {
times <- tabulate(week, 4)
vector <-
c(
1 / times[1],
1 - 1 / times[1],
1 / times[2],
1 - 1 / times[2],
1 / times[3],
1 - 1 / times[3],
1 / times[4],
1 - 1 / times[4]
)
vector
})
}
Other implementations to consider are of course sweep, but for now this works..