I have a large matrix with a column of datetime information.
The structure is: '2022-01-01_0545'(no seconds).
I'm looking for an effective way to get the number of occurrences of each year, month and day in my matrix. What could be a good approach?
Could I use the table() function or is it better to split the string into its components?
Example:
dates <- c("2022-01-01_0545","2022-03-01_0810","2021-12-13_1003","2022-09-10_0400","2022-03-09_1802")
data <- matrix(0 , nrow = 5, ncol = 2)
data <- cbind(data, dates)
colnames(data) <- NULL
Another example using dput(data[1:5, 10:11):
structure(c("290.603961274028", "281.885433495045", "283.438215255737",
"275.935544893146", "284.739524498582", "2018-01-01_0000", "2018-01-03_0445",
"2018-03-07_0045", "2018-01-04_0700", "2018-02-09_0015"), dim = c(5L,
2L))
Calling your matrix m, here's using substr to extract the components and table() to make tables.
years = substr(m[, 2], 1, 4)
months = substr(m[, 2], 6, 7)
days = substr(m[, 2], 9, 10)
table(years)
# years
# 2018
# 5
table(months)
# months
# 01 02 03
# 3 1 1
table(days)
# days
# 01 03 04 07 09
# 1 1 1 1 1