Assign unique nums to groups in data.table

Programming
,
1

Rewritten

I have a data.table with different groups and objects within each group, where each row is an object. Each object has a start and an end value. I want to do the following:

  1. Create a new column containing all the numbers between the start and end values.
  2. Group the data.table by group and get the unique numbers.
  3. Count the unique numbers for each group, accounting for overlapping numbers.

For example, for group a the result should be:

group | (old cols) | numbers | unique_number_per_group | count_unique_numbers
"a"   | ...        | 3 4 5 6 7 8 9 | 3 4 5 6 7 8 9 10 11 15 16 17 18 19 20 | 15
2

To achieve the desired result, you can use the following code:

library(data.table)

# Create a sample data.table
dt <- data.table(
  group = c("a", "a", "b", "b"),
  start = c(3, 10, 5, 15),
  end = c(9, 20, 8, 20)
)

# Step 1: Create a new column containing all the numbers between start and end values
dt[, numbers := list(seq(start, end)), by = group]

# Step 2: Group the data.table by group and get the unique numbers
dt[, unique_numbers := unique(unlist(numbers)), by = group]

# Step 3: Count the unique numbers for each group, accounting for overlapping numbers
dt[, count_unique_numbers := length(unique_numbers), by = group]

# Print the final result
dt

This code will generate the desired output, where the numbers column contains all the numbers between the start and end values, the unique_numbers column contains the unique numbers for each group, and the count_unique_numbers column contains the count of unique numbers for each group.

Note: Make sure you have the data.table package installed. If not, you can install it using install.packages("data.table").