updatedFix

require(zoo)
require(chron)
setwd("/home/knavero/Desktop/")

fmt = "%m/%d/%Y %H:%M"
tail1 = function(x) tail(x, 1)
rawData = read.zoo("weatherData.txt", header = T, FUN = as.chron,
   format = fmt, sep = "\t", aggregate = tail1)

temp = as.numeric(as.vector(rawData))
rawData = suppressWarnings(zoo(cbind(temp = temp),
   time(rawData)))

oneMin = seq(start(rawData), end(rawData), by = times("00:01:00"))
intData = (na.approx(rawData, xout = oneMin))

#par(mfrow = c(3, 1), oma = c(0, 0, 2, 0), mar = c(1, 4, 1, 1))

#suppressWarnings(plot(rawData, type = "p", ylim = c(0, 100)))
#grid(col = "darkgrey")

#plot(intData, type = "p", ylim = c(0, 100))
#grid(col = "darkgrey")

min = times("00:15:00")
offset = min*1/2
avgData = suppressWarnings(aggregate(intData, trunc(time(intData) + offset, min), mean))

#plot(avgData, type = "p", ylim = c(0, 100))
#grid(col = "darkgrey")