You can compute the average difference between the timestamps, and check if it is closer to 1 (daily data), 7 (weekly), etc.
guess_period <- function(x) {
average_period <- as.double( mean(diff(index(x))), units="days" )
difference <- abs(log( average_period / c(
daily = 1,
business_days = 7/5,
weekly = 7,
monthly = 30,
quarterly = 365/4,
annual = 365
) ) )
names( which.min( difference ) )
}
# Examples
library(quantmod)
getSymbols("^GSPC")
guess_period( GSPC )
# [1] "business_days"
getSymbols('CPIAUCNS',src='FRED')
guess_period( CPIAUCNS )
# [1] "monthly"