xts (version 0.0-6)

to.period: Convert time series data to an OHLC series

Description

Convert an OHLC or univariate object to a specified periodicity lower than the given data object. For example, convert a daily series to a monthly series, or a monthly series to a yearly one, or a one minute series to an hourly series.

The result will contain the open and close for the given period, as well as the maximum and minimum over the new period, reflected in the new high and low, respectively.

If volume for a period was available, the new volume will also be calculated.

Usage

to.minutes(x,k,name,...)
to.minutes3(x,name,...)
to.minutes5(x,name,...)
to.minutes10(x,name,...)
to.minutes15(x,name,...)
to.minutes30(x,name,...)
to.hourly(x,name,...)
to.daily(x,drop.time=TRUE,name,...)
to.weekly(x,drop.time=TRUE,name,...)
to.monthly(x,indexAt='yearmon',drop.time=FALSE,name,...)
to.quarterly(x,indexAt='yearqtr',drop.time=FALSE,name,...)
to.yearly(x,drop.time=TRUE,name,...)
to.period(x, period = 'months', k = 1, indexAt, name=NULL, ...)

Arguments

x

a univariate or OHLC type time-series object

period

period to convert to. See details.

indexAt

convert final index to new class or date. See details

drop.time

remove time component of POSIX datestamp (if any)

k

number of sub periods to aggregate on (only for minutes and seconds)

name

override column names

...

additional arguments

Value

• An object of the original type, with new periodicity.

Details

Essentially an easy and reliable way to convert one periodicity of data into any new periodicity. It is important to note that all dates will be aligned to the end of each period by default - with the exception of to.monthly and to.quarterly, which index by yearmon and yearqtr from the zoo package, respectively.

Valid period character strings include: "seconds", "minutes", "hours", "days", "weeks", "months", "quarters", and "years". These are calclated internally via endpoints. See that function's help page for further details.

To adjust the final indexing style, it is possible to set indexAt to one of the following: yearmon, yearqtr, firstof, lastof, startof, or endof. The final index will then be yearmon, yearqtr, the first time of the period, the last time of the period, the starting time in the data for that period, or the ending time in the data for that period, respectively.

It is also possible to pass a single time series, such as a univariate exchange rate, and return an OHLC object of lower frequency - e.g. the weekly OHLC of the daily series.

Setting drop.time to TRUE (the default) will convert a series that includes a time component into one with just a date index, as the time index is often of little value in lower frequency series.

It is not possible to convert a series from a lower periodicity to a higher periodicity - e.g. weekly to daily or daily to 5 minute bars, as that would require magic.

Examples

# download daily US/EU exchange rate from
# the FRED system
library(quantmod)
getSymbols("DEXUSEU",src="FRED")
getSymbols("QQQQ",src="yahoo")

# look at the data : )
DEXUSEU   # univariate time series
QQQQ      # OHLC already

# now it's a yearly OHLC
dex1 <- to.yearly(DEXUSEU)

# first monthly, then to yearly
dex2 <- to.yearly(to.monthly(DEXUSEU))

identical(dex1,dex2) # it's the same!

q1 <- to.yearly(QQQQ)
q2 <- to.yearly(to.monthly(QQQQ))

# these don't match - sometimes dates
# are off depending on when cutoffs
# occur - so BE CAREFUL when converting
# a converted object!
identical(q1,q2)