| read.zoo {zoo} | R Documentation |
read.zoo and write.zoo are convenience functions for reading
and writing "zoo" series from/to text files. They are convenience
interfaces to read.table and write.table, respectively.
read.zoo(file, format = "", tz = "", FUN = NULL, regular = FALSE, index.column = 1, drop = TRUE, FUN2 = NULL, split = NULL, aggregate = FALSE, ...) write.zoo(x, file = "", index.name = "Index", row.names = FALSE, col.names = NULL, ...)
file |
character giving the name of the file which the data
are to be read from/written to. See read.table and
write.table for more information. Alternatively,
in read.zoo, file can be a data.frame (e.g.,
resulting from a previous read.table call) that
is subsequently processed to a "zoo" series. |
format |
date format argument passed to FUN. |
tz |
time zone argument passed to as.POSIXct. |
FUN |
a function for computing the index from the first column of the data. See details. |
regular |
logical. Should the series be coerced to class "zooreg"
(if the series is regular)? |
index.column |
integer. The column of the data frame in which the index/time is stored. |
drop |
logical. If the data frame contains just a single data column, should the second dimension be dropped? |
x |
a "zoo" object. |
index.name |
character with name of the index column in the written data file. |
row.names |
logical. Should row names be written? Default is FALSE
because the row names are just character representations of the index. |
col.names |
logical. Should column names be written? Default is to
write column names only if x has column names. |
FUN2 |
function. It is applied to the time index after
FUN and before aggregate. |
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
reshape command for description of long data.
If split=Inf then the first of each run are made into a separate
series, the second of each run and so on. If split= -Inf then
the last of each run is made into a separate series, the second last
and so on.
|
aggregate |
logical or function. If set to TRUE, then aggregate.zoo
is applied to the zoo object created to compute the mean of all values with
the same time index. Alternatively, aggregate can be set to any other
function that should be used for aggregation.
If FALSE (the default), no aggregation is performed and a warning
is given if there are any duplicated time indexes. Note that most
zoo functions do not accept objects with duplicate time indexes.
See aggregate.zoo. |
... |
further arguments passed to read.table or
write.table, respectively. |
read.zoo is a convenience function which should make it easier
to 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 is
interpreted 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 and
1, 2, ... are used for the index.) To assign the appropriate class
to the index, FUN can be specified and is applied to the first column.
To process the index, read.zoo uses the first of the following that is
true: 1. If FUN is specified then read.zoo calls FUN with
the index as the first argument. 2. If tz is specified then the index
column is converted to POSIXct. 3. If format is specified
then the index column is converted to Date. 4. A heuristic
attempts to decide among "numeric", "Date" and "POSIXct".
If format and/or tz is specified
then it is passed to the conversion function as well.
If regular is set to TRUE and the resulting series has an
underlying regularity, it is coerced to a "zooreg" series.
write.zoo is a convenience function for writing "zoo" series
to text files. It first coerces its argument to a "data.frame", adds
a column with the index and then calls write.table.
read.zoo returns an object of class "zoo" (or "zooreg").
read.zoo works by first reading the data in using read.table
and then processing it. This implies that
if the index field is entirely numeric the default is to pass it to FUN
or the built-in date conversion routine
a number, rather than a character string.
Thus, a date field such as 09122007 intended
to represent December 12, 2007 would be seen as 9122007
and 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 fact
it would receive
2000.1 and regard it as the first month of 2000
unless similar precautions were taken.
In the above cases the index field should be specified to be
"character" so that leading or trailing zeros
are 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.
## Not run:
## turn *numeric* first column into yearmon index
## where number is year + fraction of year represented by month
z <- 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 2
z <- read.zoo("foo.tab", format = "%m/%d/%Y")
# Suppose lines look like: 09112007 1 2 and there is no header
z <- 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)
## End(Not run)
## omit the read.table() phase and directly supply a data.frame
dat <- data.frame(date = paste("2000-01-", 10:15, sep = ""), a = rnorm(6), b = 1:6)
z <- read.zoo(dat)
## using built-in data frame BOD
read.zoo(BOD)
read.zoo(BOD, FUN = as.Date)
read.zoo(BOD[c(1:6, 1), ], aggregate = mean)