| read.zoo {zoo} | R Documentation |
Description
read.zoo and write.zoo are convenience functions for readingand writing "zoo" series from/to text files. They are convenienceinterfaces to read.table and write.table, respectively.To employ read.csv, read.csv2, read.delim,read.delim2 instead of read.table additional functionsread.csv.zoo etc. are provided.
Usage
read.zoo(file, format = "", tz = "", FUN = NULL, regular = FALSE, index.column = 1, drop = TRUE, FUN2 = NULL, split = NULL, aggregate = FALSE, ..., text, read = read.table) write.zoo(x, file = "", index.name = "Index", row.names = FALSE, col.names = NULL, ...)read.csv.zoo(..., read = read.csv)read.csv2.zoo(..., read = read.csv2)read.delim.zoo(..., read = read.delim)read.delim2.zoo(..., read = read.delim2)Arguments
file | character string or strings giving the name of the file(s) which the dataare to be read from/written to. See |
format | date format argument passed to |
tz | time zone argument passed to |
FUN | a function for computing the index from the first columnof the data. See details. |
regular | logical. Should the series be coerced to class |
index.column | numeric vector or list. The column names or numbers of the data frame in which the index/time is stored. If the |
drop | logical. If the data frame contains just a single data column, shouldthe second dimension be dropped? |
x | a |
index.name | character with name of the index column in the writtendata file. |
row.names | logical. Should row names be written? Default is |
col.names | logical. Should column names be written? Default is towrite column names only if |
FUN2 | function. It is applied to the time index after |
split | NULL or column number or name or vector of numbers or names. If not NULL then the data is assumed to be in long format and is split according to the indicated columns. See the R |
aggregate | logical or function. If set to |
... | further arguments passed to other functions. In the |
text | character. If |
read | function. The function for reading |
Details
read.zoo is a convenience function which should make it easierto read data from a text file and turn it into a "zoo" series immediately. read.zoo reads the data file via read.table(file, ...).The column index.column (by default the first) of the resulting data isinterpreted to be the index/time, the remaining columns the corresponding data.(If the file only has only column then that is assumed to be the data column and1, 2, ... are used for the index.) To assign the appropriate classto the index, FUN can be specified and is applied to the first column.
To process the index, read.zoo calls FUN with the index as thefirst argument. If FUN is not specified, the following default is employed:
(a) If file is a data frame with a singleindex column that appears to be a time index already, then FUN = identity is used.The conditions for a readily produced time index are: It is not character or factor (and the arguments tz and format must not be specified).
(b) If the conditions from (a) do not hold then the following strategy is used.If there are multiple index columns they are pasted together with a space between each.Using the (pasted) index column: (1) If tz is specified then theindex column is converted to POSIXct. (2) If format is specifiedthen the index column is converted to Date. (3) Otherwise, a heuristicattempts to decide between "numeric", "POSIXct", and "Date" bytrying them in that order (which may not always succeed though). By default,only the standard date/time format is used. Hence, supplying format and/or tzis necessary if some date/time format is used that is not the default. And evenif the default format is appropriate for the index, explicitly supplyingFUN or at least format and/or tz typically leads to morereliable results than the heuristic.
If regular is set to TRUE and the resulting series has an underlying regularity, it is coerced to a "zooreg" series.
To employ other functions than read.table to read the initial data,further convenience interfaces read.csv.zoo etc. are provided.
write.zoo is a convenience function for writing "zoo" seriesto text files. It first coerces its argument to a "data.frame", addsa column with the index and then calls write.table.
See also vignette("zoo-read", package = "zoo") for detailed examples.
Value
read.zoo returns an object of class "zoo" (or "zooreg").
Note
read.zoo works by first reading the data in using read.tableand then processing it. This implies that if the index field is entirely numeric the default is to pass it to FUNor the built-in date conversion routinea number, rather than a character string. Thus, a date field such as 09122007 intendedto represent December 12, 2007 would be seen as 9122007and interpreted as the 91st day thereby generating an error.
This comment also applies to trailing decimals so that if 2000.10 were intended to represent the 10th month of 2000 in factit would receive2000.1 and regard it as the first month of 2000unless similar precautions were taken.
In the above cases the index field should be specified to be"character" so that leading or trailing zerosare not dropped. This can be done by specifying a "character"index column in the "colClasses" argument, which is passed to read.table, as shown in the examples below.
See Also
zoo
Examples
## this manual page provides a few typical examples, many more cases## are covered in vignette("zoo-read", package = "zoo")## read text lines with a single date columnLines <- "2013-12-24 22013-12-25 32013-12-26 8"read.zoo(text = Lines, FUN = as.Date) # explicit coercionread.zoo(text = Lines, format = "%Y-%m-%d") # sameread.zoo(text = Lines) # same, via heuristic## read text lines with date/time in separate columnsLines <- "2013-11-24 12:41:21 22013-12-25 12:41:22.25 32013-12-26 12:41:22.75 8"read.zoo(text = Lines, index = 1:2, FUN = paste, FUN2 = as.POSIXct) # explicit coercionread.zoo(text = Lines, index = 1:2, tz = "") # sameread.zoo(text = Lines, index = 1:2) # same, via heuristic## read text lines with month/year in separate columnsLines <- "Jan 1998 4.36Feb 1998 4.34"read.zoo(text = Lines, index = 1:2, FUN = paste, FUN2 = as.yearmon)## read directly from a data.frame (artificial and built-in BOD)dat <- data.frame(date = paste("2000-01-", 10:15, sep = ""), a = sin(1:6), b = cos(1:6))read.zoo(dat)data("BOD", package = "datasets")read.zoo(BOD)## Not run: ## descriptions of typical examples## turn *numeric* first column into yearmon index## where number is year + fraction of year represented by monthz <- read.zoo("foo.csv", sep = ",", FUN = as.yearmon)## first column is of form yyyy.mm## (Here we use format in place of as.character so that final zero ## is not dropped in dates like 2001.10 which as.character would do.)f <- function(x) as.yearmon(format(x, nsmall = 2), "%Y.%m")z <- read.zoo("foo.csv", header = TRUE, FUN = f)## turn *character* first column into "Date" index## Assume lines look like: 12/22/2007 1 2z <- read.zoo("foo.tab", format = "%m/%d/%Y")# Suppose lines look like: 09112007 1 2 and there is no headerz <- read.zoo("foo.txt", format = "%d%m%Y")## csv file with first column of form YYYY-mm-dd HH:MM:SS## Read in times as "chron" class. Requires chron 2.3-22 or later.z <- read.zoo("foo.csv", header = TRUE, sep = ",", FUN = as.chron)## same but with custom format. Note as.chron uses POSIXt-style ## Read in times as "chron" class. Requires chron 2.3-24 or later.z <- read.zoo("foo.csv", header = TRUE, sep = ",", FUN = as.chron, format = "## same file format but read it in times as "POSIXct" class.z <- read.zoo("foo.csv", header = TRUE, sep = ",", tz = "")## csv file with first column mm-dd-yyyy. Read times as "Date" class.z <- read.zoo("foo.csv", header = TRUE, sep = ",", format = "%m-%d-%Y")## whitespace separated file with first column of form YYYY-mm-ddTHH:MM:SS## and no headers. T appears literally. Requires chron 2.3-22 or later.z <- read.zoo("foo.csv", FUN = as.chron)# read in all csv files in the current directory and merge themread.zoo(Sys.glob("*.csv"), header = TRUE, sep = ",")# We use "NULL" in colClasses for those columns we don't need but in # col.names we still have to include dummy names for them. Of what # is left the index is the first three columns (1:3) which we convert # to chron class times in FUN and then truncate to 5 seconds in FUN2. # Finally we use aggregate = mean to average over the 5 second intervals.library("chron")Lines <- "CVX 20070201 9 30 51 73.25 81400 0CVX 20070201 9 30 51 73.25 100 0CVX 20070201 9 30 51 73.25 100 0CVX 20070201 9 30 51 73.25 300 0CVX 20070201 9 30 51 73.25 81400 0CVX 20070201 9 40 51 73.25 100 0CVX 20070201 9 40 52 73.25 100 0CVX 20070201 9 40 53 73.25 300 0"z <- read.zoo(text = Lines, colClasses = c("NULL", "NULL", "numeric", "numeric", "numeric", "numeric", "numeric", "NULL"), col.names = c("Symbol", "Date", "Hour", "Minute", "Second", "Price", "Volume", "junk"), index = 1:3, # do not count columns that are "NULL" in colClasses FUN = function(h, m, s) times(paste(h, m, s, sep = ":")), FUN2 = function(tt) trunc(tt, "00:00:05"), aggregate = mean)## End(Not run)[Package zoo version 1.8-12 Index]
