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ROracle and select query empty

5 messages · Mathieu Drapeau, David James, Philippe GROSJEAN +2 more

#
Hi,
I just installed ROracle and RDBI. The connection to the database seems 
to work also. My problem is when I am selection rows that really exist 
in the database, it is returning nothing. Where should I look to see 
what could be my problem?

Thank you very much,
Mathieu

 > drv <- dbDriver("Oracle")
 > summary(drv, verbose=TRUE)
<OraDriver:(6721)>
  Driver name:  Oracle (ProC/C++)
  Max  connections: 10
  Conn. processed: 8
  Default records per fetch: 500
  Oracle R/S client version: 0.5-4
  RS-DBI version:  0.1-9
  Open connections: 2
    1  <OraConnection:(6721,0)>
    2  <OraConnection:(6721,7)>
 >
 > conn <- dbConnect(drv, "mathieu/toto at MYDB")
 > summary(conn, verbose=TRUE) <OraConnection:(6721,7)>
  User: mathieu
  Dbname: MYDB
  Oracle Server version:
 >
 > rs <- dbSendQuery(conn, statement = paste("select * from cat"))
 > summary(rs, verbose=TRUE)
<OraResult:(6721,7,2)>
  Statement: select * from cat
  Has completed? no
  Affected rows: 0
  Rows fetched: -1
  Fields:
        name    Sclass     type len precision scale isVarLength nullOK
1 TABLE_NAME character VARCHAR2  30         0     0        TRUE  FALSE
2 TABLE_TYPE character VARCHAR2  11         0     0        TRUE   TRUE
 >
 > myContent <- fetch(rs, n = -1)
 > myContent
[1] TABLE_NAME TABLE_TYPE
<0 rows> (or 0-length row.names)
 > summary(myContent, verbose=TRUE)
  TABLE_NAME         TABLE_TYPE
 Length:0           Length:0
 Class :character   Class :character
 Mode  :character   Mode  :character
 > summary(rs, verbose=TRUE)
<OraResult:(6721,7,2)>
  Statement: select * from cat
  Has completed? yes
  Affected rows: 0
  Rows fetched: -1
  Fields:
        name    Sclass     type len precision scale isVarLength nullOK
1 TABLE_NAME character VARCHAR2  30         0     0        TRUE  FALSE
2 TABLE_TYPE character VARCHAR2  11         0     0        TRUE   TRUE
#
Hello,

I'm working with irregular time series data.  What do you all think  
about the strengths and weaknesses of the "zoo" and "its" packages?

I've installed and skimmed the documentation on both packages.  I was  
hoping to get a little guidance from the user community before  
proceeding further.

In case anyone is interested in my particular problem:  I'm looking  
at some (surface) temperature data from NOAA:  http:// 
cdo.ncdc.noaa.gov/ulcd/ULCD
It is (irregular) time series format.  The NOAA data reports year,  
month, date, hour, and minute.  I want to group the data into hourly  
chunks.  However, sometimes there are multiple observation per hour  
-- i.e an observation at 3:45 and 3:56.  Also, sometimes a particular  
hour may be missing altogether.  I need to clean up the data so that  
each hour has one and only one data point.

I'm relatively new to R, but I think I'm getting a hold on it pretty  
well so far.  I used to do a lot with MATLAB, and there seem to be  
many parallels between it and R.  I have background in public policy  
and econometrics.

Thanks,
David
On Aug 25, 2005, at 12:29 PM, Mathieu Drapeau wrote:

            
#
Hello David,

You may be interested also by the regul() function and similar fro the 
pastecs package: it is designed to solve the kind of problems you talk 
about. You should read the manual, which is included. However, this 
manual is in French.
Best,

Philippe

..............................................<??}))><........
  ) ) ) ) )
( ( ( ( (    Prof. Philippe Grosjean
  ) ) ) ) )
( ( ( ( (    Numerical Ecology of Aquatic Systems
  ) ) ) ) )   Mons-Hainaut University, Pentagone (3D08)
( ( ( ( (    Academie Universitaire Wallonie-Bruxelles
  ) ) ) ) )   8, av du Champ de Mars, 7000 Mons, Belgium
( ( ( ( (
  ) ) ) ) )   phone: + 32.65.37.34.97, fax: + 32.65.37.30.54
( ( ( ( (    email: Philippe.Grosjean at umh.ac.be
  ) ) ) ) )
( ( ( ( (    web:   http://www.umh.ac.be/~econum
  ) ) ) ) )          http://www.sciviews.org
( ( ( ( (
..............................................................
David James wrote:
#
On 8/25/05, David James <djames at frontierassoc.com> wrote:
I have worked on the development of zoo with Achim Zeileis so
I will just speak to that one.

The key to notice about zoo is its independence of index class
(i.e.  date, time or date/time class) making it general in
nature so that you can use any one you like.  It supports
all the standard date and time classes in R and you can add
your own too. In your case you probably want to use chron
(or POSIXct if you need time zones) or you could create your 
own special hourly class.  See the Help Desk article in 
R News 4/1 for a discussion of the main classes and
see the table at the end of that article for various idioms which 
you may need.

zoo supports not only irregular but also weakly regular
series (zooreg class) which are ones that have an underlying 
regularity, e.g. hourly, monthly even though they may not
have every hour, month, etc. filled in.

zoo has a PDF manual available via (in R):

   library(zoo)
   vignette("zoo")

zoo can work together with the 'its' class and 'ts' class via as.zoo, 
as.its and as.ts.
Using the chron date/time class here is an example:

library(chron)
library(zoo)

set.seed(1)

# create zoo series with random dates/times between tt0 and tt1 
# also random values
set.seed(1)
n <- 25
tt0 <- chron("01/01/90")
tt1 <- chron("01/01/00")
tt <- sort(as.numeric(tt1-tt0)*runif(n)+tt0)
z <- zoo(rnorm(n), tt)  # create zoo series from values and date/times

# aggregate by hour choosing first data point if there are mulitples.
# The arguments are (1) the zoo series (2) time rounded to the hour
# (3) aggregate function to use -- indexing in this case, (4) an
# argument to the indexing function -- in this case its 1 since
# we want the first element.  See ?aggregate.zoo
z.hr <- aggregate(z, chron(floor(24*as.numeric(tt))/24), "[", 1)

# plot hourly series, see ?plot.zoo
plot(z.hr) 

Packages with explicit support for zoo are strucchange, dynlm
and dyn.  (dyn also supports ts and its.)
Check out 
   http://cran.r-project.org/doc/contrib/R-and-octave-2.txt
Check out
   http://cran.r-project.org/src/contrib/Views/
1 day later
#
Mathieu Drapeau <mathieu.drapeau at mcgill.ca> wrote:
What platform are you running R on?  And what version of Oracle?  This
sounds very familiar... are you building ROracle on Linux?

-- David Hinds