library(quantmod)

env <- new.env()
Symbols <- c('ECA', 'DDD', 'MO', 'RHT')
getSymbols(Symbols = Symbols, env = env, from = Sys.Date() - 365)
## [1] "ECA" "DDD" "MO"  "RHT"
args <- eapply(env = env, FUN = function(x){Ad(x)})[Symbols]
prices <- na.omit(do.call(what = merge, args = args))
colnames(prices) <- Symbols

## get 52 week high ----
max <- as.vector(apply(prices, 2, max))

## get latest price
last <- as.vector(prices[dim(prices)[1], ])

## % below 52 week high ----
perBelow <- last / max - 1
names(perBelow) <- Symbols

perBelow
##         ECA         DDD          MO         RHT 
## -0.69965520 -0.76818665 -0.02041187 -0.12640976