Non-redundant version of expand.grid
Sure! Here is an example of how to create a non-redundant version of the expand.grid
function in R, along with explanations for each step.
nonredundant_expand.grid <- function(...) {
args <- list(...)
# Step 1: Get the number of arguments and their lengths
num_args <- length(args)
arg_lengths <- sapply(args, length)
# Step 2: Create an empty matrix to store the combinations
result <- matrix(nrow = prod(arg_lengths), ncol = num_args)
# Step 3: Fill in the matrix with the combinations
for (i in 1:num_args) {
result[, i] <- rep.int(rep.int(args[[i]], each = prod(arg_lengths[-i])), times = prod(arg_lengths[-(1:i)]))
}
# Step 4: Return the matrix as a data frame
as.data.frame(result)
}
Step 1: Get the number of arguments and their lengths
In this step, we use the list
function to convert the arguments passed to the function into a list. We then use the length
function to get the number of arguments and the sapply
function to get the lengths of each argument.
Step 2: Create an empty matrix to store the combinations
In this step, we use the matrix
function to create an empty matrix with the number of rows equal to the product of the lengths of all the arguments and the number of columns equal to the number of arguments.
Step 3: Fill in the matrix with the combinations
In this step, we use a for loop to iterate over each argument. For each argument, we use the rep.int
function to repeat the values of that argument, with the number of repetitions determined by the product of the lengths of all the other arguments. We then use the rep.int
function again to repeat the resulting vector, with the number of repetitions determined by the product of the lengths of all the arguments after the current argument. We fill in the corresponding column of the matrix with the resulting vector.
Step 4: Return the matrix as a data frame
In this step, we use the as.data.frame
function to convert the matrix into a data frame and return it as the result of the function.
I hope this helps! Let me know if you have any further questions.