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Ajay Shah

2004-Feb-23 20:07 UTC

[R] Need help on parsing dates

I know this:

  > library(date)
  > x="1979-04-04"
  > try=as.date(x, "ymd")
  > print(try)
  [1] 4Apr79

and that `x' here has to be a string, e.g.:

  > x=1979-04-04
  > print(x)
  [1] 1971

I'm stuck in reading from a file. I say:  

  > A <- read.table(file="try")
  > print(A)
             V1          V2
  1  1979-04-04 -1.04712042
  2  1979-04-06  0.54538055
  3  1979-04-09  0.09663392
  4  1979-04-11  0.57119871
  5  1979-04-12  0.73594112
  6  1979-04-17 -1.54422087
  7  1979-04-18 -0.20595691
  8  1979-04-19  0.12700429
  9  1979-04-20  0.42016807
  10 1979-04-23 -1.46838241

I am confused - is V1 a number or a string? Looking at it, it must be
a string. But yet:

  > library(date)
  > try=as.date(A$V1, "ymd")
  Error in as.date(A$V1, "ymd") : Cannot coerce to date format

In short, how do I parse in dates of the format yyyy-mm-dd (the ISO
8601 format) or the yyyymmdd format.

And if I may ask the next step: How do I tell R that I have a file
full of data all of which is time-series data, where V1 is the
datetime vector, and all the other columns are time-series, to do
things like ARMA models and ts plots with?

-- 
Ajay Shah                                                   Consultant
ajayshah at mayin.org                      Department of Economic Affairs
http://www.mayin.org/ajayshah           Ministry of Finance, New Delhi

Prof Brian Ripley

2004-Feb-23 20:16 UTC

head link

[R] Need help on parsing dates

On Tue, 24 Feb 2004, Ajay Shah wrote:
> I know this:
> 
>   > library(date)
>   > x="1979-04-04"
>   > try=as.date(x, "ymd")
>   > print(try)
>   [1] 4Apr79
> 
> and that `x' here has to be a string, e.g.:
> 
>   > x=1979-04-04
>   > print(x)
>   [1] 1971
> 
> I'm stuck in reading from a file. I say:  
> 
>   > A <- read.table(file="try")
>   > print(A)
>              V1          V2
>   1  1979-04-04 -1.04712042
>   2  1979-04-06  0.54538055
>   3  1979-04-09  0.09663392
>   4  1979-04-11  0.57119871
>   5  1979-04-12  0.73594112
>   6  1979-04-17 -1.54422087
>   7  1979-04-18 -0.20595691
>   8  1979-04-19  0.12700429
>   9  1979-04-20  0.42016807
>   10 1979-04-23 -1.46838241
> 
> I am confused - is V1 a number or a string? Looking at it, it must be
> a string. But yet:
It is a factor.  See ?read.table.>   > library(date)
>   > try=as.date(A$V1, "ymd")
>   Error in as.date(A$V1, "ymd") : Cannot coerce to date format
> 
> In short, how do I parse in dates of the format yyyy-mm-dd (the ISO
> 8601 format) or the yyyymmdd format.
> 
> And if I may ask the next step: How do I tell R that I have a file
> full of data all of which is time-series data, where V1 is the
> datetime vector, and all the other columns are time-series, to do
> things like ARMA models and ts plots with?
You can't with an irregular series like this one.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

Sundar Dorai-Raj

2004-Feb-23 20:16 UTC

head link

[R] Need help on parsing dates

Ajay Shah wrote:
> I know this:
> 
>   > library(date)
>   > x="1979-04-04"
>   > try=as.date(x, "ymd")
>   > print(try)
>   [1] 4Apr79
> 
> and that `x' here has to be a string, e.g.:
> 
>   > x=1979-04-04
>   > print(x)
>   [1] 1971
> 
> I'm stuck in reading from a file. I say:  
> 
>   > A <- read.table(file="try")
>   > print(A)
>              V1          V2
>   1  1979-04-04 -1.04712042
>   2  1979-04-06  0.54538055
>   3  1979-04-09  0.09663392
>   4  1979-04-11  0.57119871
>   5  1979-04-12  0.73594112
>   6  1979-04-17 -1.54422087
>   7  1979-04-18 -0.20595691
>   8  1979-04-19  0.12700429
>   9  1979-04-20  0.42016807
>   10 1979-04-23 -1.46838241
> 
> I am confused - is V1 a number or a string? Looking at it, it must be
> a string. But yet:
> 
>   > library(date)
>   > try=as.date(A$V1, "ymd")
>   Error in as.date(A$V1, "ymd") : Cannot coerce to date format
> 
> In short, how do I parse in dates of the format yyyy-mm-dd (the ISO
> 8601 format) or the yyyymmdd format.
> 
> And if I may ask the next step: How do I tell R that I have a file
> full of data all of which is time-series data, where V1 is the
> datetime vector, and all the other columns are time-series, to do
> things like ARMA models and ts plots with?
> 
To see what class a column in a data.frame is the best way is to try:

sapply(A, data.class)

My guess is that "V1" is being read in as a factor (default). To
convert
to character to use with as.date, then use

as.date(as.character(A$V1), "ymd")

BTW, I would avoid using "try" as a variable name since
"try" is a
function in the base package.

As for you second question, see the package ts for ARIMA
modeling.

-sundar

Don MacQueen

2004-Feb-23 20:28 UTC

head link

[R] Need help on parsing dates

At 1:37 AM +0530 2/24/04, Ajay Shah wrote:>I know this:
>
>   > library(date)
>   > x="1979-04-04"
>   > try=as.date(x, "ymd")
>   > print(try)
>   [1] 4Apr79
>
>and that `x' here has to be a string, e.g.:
>
>   > x=1979-04-04
>   > print(x)
>   [1] 1971
>
>I'm stuck in reading from a file. I say: 
>
>   > A <- read.table(file="try")
>   > print(A)
>              V1          V2
>   1  1979-04-04 -1.04712042
>   2  1979-04-06  0.54538055
>   3  1979-04-09  0.09663392
>   4  1979-04-11  0.57119871
>   5  1979-04-12  0.73594112
>   6  1979-04-17 -1.54422087
>   7  1979-04-18 -0.20595691
>   8  1979-04-19  0.12700429
>   9  1979-04-20  0.42016807
>   10 1979-04-23 -1.46838241
>
>I am confused - is V1 a number or a string? Looking at it, it must be
>a string. But yet:
You can find out what it is by asking:
   mode(A$V1)
   class(A$V1)
   str(A$V1)
and there are no doubt some other ways to ask.
>
>   > library(date)
>   > try=as.date(A$V1, "ymd")
>   Error in as.date(A$V1, "ymd") : Cannot coerce to date format
>
>In short, how do I parse in dates of the format yyyy-mm-dd (the ISO
>8601 format) or the yyyymmdd format.
>
>And if I may ask the next step: How do I tell R that I have a file
>full of data all of which is time-series data, where V1 is the
>datetime vector, and all the other columns are time-series, to do
>things like ARMA models and ts plots with?
>
>--
>Ajay Shah                                                   Consultant
>ajayshah at mayin.org                      Department of Economic Affairs
>http://www.mayin.org/ajayshah           Ministry of Finance, New Delhi
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://www.stat.math.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html

-- 
--------------------------------------
Don MacQueen
Environmental Protection Department
Lawrence Livermore National Laboratory
Livermore, CA, USA

Gabor Grothendieck

2004-Feb-23 22:22 UTC

head link

[R] Need help on parsing dates

There are a number of ways to do this.  First read in the data 
using the as.is=1 argument to ensure that the date is read 
in as character:

   z <- read.table(myfile, as.is=1, sep=" ",
col.names=c("Date", "Data"))

Now you can create a date column using date, POSIXct, chron or irts:

   # date
   require(date)  
   z$Date <- as.date(z$Date,format="ymd"))

   # POSIXct
   z$Date <- as.POSIXct(z$Date))

   # chron
   require(chron)
   z$Date <- chron(z$Date, "y-m-d")

You can create a ts timeseries (which is regular) by ignoring t
he dates altogether:

   z.ts <- ts(z$Data)

Or an irts irregular time series using package tseries:

   require(tseries)
   z.irts <- irts(as.POSIXct(z$Date), z$Data)

Or an its irregular time series using package its:

   require(its)
   z.its <- readcsvIts(myfile, sep=" ",
col.names=c("Date", "Data"))

Assuming z.ts was used you can do this:

ar(z.ts, order=1)
etc.

---
Date:   Tue, 24 Feb 2004 01:37:23 +0530 
From:   Ajay Shah <ajayshah at mayin.org>
To:   r-help <r-help at stat.math.ethz.ch> 
Subject:   [R] Need help on parsing dates 

 
I know this:
> library(date)
> x="1979-04-04"
> try=as.date(x, "ymd")
> print(try)[1] 4Apr79

and that `x' here has to be a string, e.g.:
> x=1979-04-04
> print(x)[1] 1971

I'm stuck in reading from a file. I say: 
> A <- read.table(file="try")
> print(A)V1 V2
1 1979-04-04 -1.04712042
2 1979-04-06 0.54538055
3 1979-04-09 0.09663392
4 1979-04-11 0.57119871
5 1979-04-12 0.73594112
6 1979-04-17 -1.54422087
7 1979-04-18 -0.20595691
8 1979-04-19 0.12700429
9 1979-04-20 0.42016807
10 1979-04-23 -1.46838241

I am confused - is V1 a number or a string? Looking at it, it must be
a string. But yet:
> library(date)
> try=as.date(A$V1, "ymd")Error in as.date(A$V1, "ymd") : Cannot coerce to date format

In short, how do I parse in dates of the format yyyy-mm-dd (the ISO
8601 format) or the yyyymmdd format.

And if I may ask the next step: How do I tell R that I have a file
full of data all of which is time-series data, where V1 is the
datetime vector, and all the other columns are time-series, to do
things like ARMA models and ts plots with?

Jean Eid

2004-Feb-24 01:06 UTC

head link

[R] Need help on parsing dates

?as.POSIXlt

On Tue, 24 Feb 2004, Ajay Shah wrote:
> I know this:
>
>   > library(date)
>   > x="1979-04-04"
>   > try=as.date(x, "ymd")
>   > print(try)
>   [1] 4Apr79
>
> and that `x' here has to be a string, e.g.:
>
>   > x=1979-04-04
>   > print(x)
>   [1] 1971
>
> I'm stuck in reading from a file. I say:
>
>   > A <- read.table(file="try")
>   > print(A)
>              V1          V2
>   1  1979-04-04 -1.04712042
>   2  1979-04-06  0.54538055
>   3  1979-04-09  0.09663392
>   4  1979-04-11  0.57119871
>   5  1979-04-12  0.73594112
>   6  1979-04-17 -1.54422087
>   7  1979-04-18 -0.20595691
>   8  1979-04-19  0.12700429
>   9  1979-04-20  0.42016807
>   10 1979-04-23 -1.46838241
>
> I am confused - is V1 a number or a string? Looking at it, it must be
> a string. But yet:
>
>   > library(date)
>   > try=as.date(A$V1, "ymd")
>   Error in as.date(A$V1, "ymd") : Cannot coerce to date format
>
> In short, how do I parse in dates of the format yyyy-mm-dd (the ISO
> 8601 format) or the yyyymmdd format.
>
> And if I may ask the next step: How do I tell R that I have a file
> full of data all of which is time-series data, where V1 is the
> datetime vector, and all the other columns are time-series, to do
> things like ARMA models and ts plots with?
>
> --
> Ajay Shah                                                   Consultant
> ajayshah at mayin.org                      Department of Economic Affairs
> http://www.mayin.org/ajayshah           Ministry of Finance, New Delhi
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>

Gabor Grothendieck

2004-Feb-25 07:48 UTC

head link

[R] Need help on parsing dates

I just came across another package for irregular dates, zoo,
giving another alternative.

It can be used together with dates, chron or POSIXct.  For
example, using chron:

require(zoo)
require(chron)
z.zoo <- zoo(z$Data, chron(z$Date, format="y-m-d"))

---
Date:   Mon, 23 Feb 2004 17:22:42 -0500 (EST) 
From:   Gabor Grothendieck <ggrothendieck at myway.com>
To:   <ajayshah at mayin.org>, <r-help at stat.math.ethz.ch> 
Subject:   RE: [R] Need help on parsing dates 

 


There are a number of ways to do this. First read in the data 
using the as.is=1 argument to ensure that the date is read 
in as character:

z <- read.table(myfile, as.is=1, sep=" ",
col.names=c("Date", "Data"))

Now you can create a date column using date, POSIXct, chron or irts:

# date
require(date) 
z$Date <- as.date(z$Date,format="ymd"))

# POSIXct
z$Date <- as.POSIXct(z$Date))

# chron
require(chron)
z$Date <- chron(z$Date, "y-m-d")

You can create a ts timeseries (which is regular) by ignoring t
he dates altogether:

z.ts <- ts(z$Data)

Or an irts irregular time series using package tseries:

require(tseries)
z.irts <- irts(as.POSIXct(z$Date), z$Data)

Or an its irregular time series using package its:

require(its)
z.its <- readcsvIts(myfile, sep=" ", col.names=c("Date",
"Data"))

Assuming z.ts was used you can do this:

ar(z.ts, order=1)
etc.

---
Date: Tue, 24 Feb 2004 01:37:23 +0530 
From: Ajay Shah <ajayshah at mayin.org>
To: r-help <r-help at stat.math.ethz.ch> 
Subject: [R] Need help on parsing dates 


I know this:
> library(date)
> x="1979-04-04"
> try=as.date(x, "ymd")
> print(try)[1] 4Apr79

and that `x' here has to be a string, e.g.:
> x=1979-04-04
> print(x)[1] 1971

I'm stuck in reading from a file. I say: 
> A <- read.table(file="try")
> print(A)V1 V2
1 1979-04-04 -1.04712042
2 1979-04-06 0.54538055
3 1979-04-09 0.09663392
4 1979-04-11 0.57119871
5 1979-04-12 0.73594112
6 1979-04-17 -1.54422087
7 1979-04-18 -0.20595691
8 1979-04-19 0.12700429
9 1979-04-20 0.42016807
10 1979-04-23 -1.46838241

I am confused - is V1 a number or a string? Looking at it, it must be
a string. But yet:
> library(date)
> try=as.date(A$V1, "ymd")Error in as.date(A$V1, "ymd") : Cannot coerce to date format

In short, how do I parse in dates of the format yyyy-mm-dd (the ISO
8601 format) or the yyyymmdd format.

And if I may ask the next step: How do I tell R that I have a file
full of data all of which is time-series data, where V1 is the
datetime vector, and all the other columns are time-series, to do
things like ARMA models and ts plots with?

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