[R] reading data from web data sources

[Gabor Grothendieck]

No one else posted so the other post you are referring to must have
been an email to you, not a post.  We did not see it.

By one off I think you are referring to the row names, which are
meaningless, rather than the day numbers.  The data for day 1 is
present, not missing.  The example code did replace the day number
column with the year since the days were just sequential and therefore
derivable but its trivial to keep them if that is important to you and
we have made that change below.

The previous code used grep to kick out lines that had any character
not in the set: minus sign, space and digit but in this version we add
minus sign to that set.   We also corrected the year column and added
column names and converted all -999 strings to NA.  Due to this last
point we cannot use na.omit any more but we now have iy available that
distinguishes between year rows and other rows.

Every line here has been indented so anything that starts at the left
column must have been word wrapped in transmission.

  myURL <- "http://climate.arm.ac.uk/calibrated/soil/dsoil100_cal_1910-1919.dat"
  raw.lines <- readLines(myURL)
  DF <- read.table(textConnection(raw.lines[!grepl("[^- 0-9.]", raw.lines)]),
    fill = TRUE, col.names = c("day", month.abb), na.strings = "-999")

  iy <- is.na(DF[[2]]) # is year row
  DF$year <- DF[iy, 1][cumsum(iy)]
  DF <- DF[!iy, ]

  DF


On Sat, Feb 27, 2010 at 3:28 PM, Tim Coote <tim+r-project.org at coote.org> wrote:
> Thanks, Gabor. My take away from this and Phil's post is that I'm going to

I think the other `post`` must have been directly to you.  We didn`t see it.

> have to construct some code to do the parsing, rather than use a standard
> function. I'm afraid that neither approach works, yet:
>
> Gabor's gets has an off-by-one error (days start on the 2nd, not the first),
> and the years get messed up around the 29th day.  I think that na.omit (DF)
> line is throwing out the baby with the bathwater.  It's interesting that
> this approach is based on read.table, I'd assumed that I'd need read.ftable,
> which I couldn't understand the documentation for.  What is it that's
> removing the -999 and -888 values in this code -they seem to be gone, but I
> cannot see why.
>
> Phil's reads in the data, but interleaves rows with just a year and all
> other values as NA.
>
> Tim
> On 27 Feb 2010, at 17:33, Gabor Grothendieck wrote:
>
>> Mark Leeds pointed out to me that the code wrapped around in the post
>> so it may not be obvious that the regular expression in the grep is
>> (i.e. it contains a space):
>> "[^ 0-9.]"
>>
>>
>> On Sat, Feb 27, 2010 at 7:15 AM, Gabor Grothendieck
>> <ggrothendieck at gmail.com> wrote:
>>>
>>> Try this.  First we read the raw lines into R using grep to remove any
>>> lines containing a character that is not a number or space.  Then we
>>> look for the year lines and repeat them down V1 using cumsum.  Finally
>>> we omit the year lines.
>>>
>>> myURL <-
>>> "http://climate.arm.ac.uk/calibrated/soil/dsoil100_cal_1910-1919.dat"
>>> raw.lines <- readLines(myURL)
>>> DF <- read.table(textConnection(raw.lines[!grepl("[^
>>> 0-9.]",raw.lines)]), fill = TRUE)
>>> DF$V1 <- DF[cumsum(is.na(DF[[2]])), 1]
>>> DF <- na.omit(DF)
>>> head(DF)
>>>
>>>
>>> On Sat, Feb 27, 2010 at 6:32 AM, Tim Coote <tim+r-project.org at coote.org>
>>> wrote:
>>>>
>>>> Hullo
>>>> I'm trying to read some time series data of meteorological records that
>>>> are
>>>> available on the web (eg
>>>> http://climate.arm.ac.uk/calibrated/soil/dsoil100_cal_1910-1919.dat).
>>>> I'd
>>>> like to be able to read in the digital data directly into R. However, I
>>>> cannot work out the right function and set of parameters to use.  It
>>>> could
>>>> be that the only practical route is to write a parser, possibly in some
>>>> other language,  reformat the files and then read these into R. As far
>>>> as I
>>>> can tell, the informal grammar of the file is:
>>>>
>>>> <comments terminated by a blank line>
>>>> [<year number on a line on its own>
>>>> <daily readings lines> ]+
>>>>
>>>> and the <daily readings> are of the form:
>>>> <whitespace> <day number> [<whitespace> <reading on day of month>] 12
>>>>
>>>> Readings for days in months where a day does not exist have special
>>>> values.
>>>> Missing values have a different special value.
>>>>
>>>> And then I've got the problem of iterating over all relevant files to
>>>> get a
>>>> whole timeseries.
>>>>
>>>> Is there a way to read in this type of file into R? I've read all of the
>>>> examples that I can find, but cannot work out how to do it. I don't
>>>> think
>>>> that read.table can handle the separate sections of data representing
>>>> each
>>>> year. read.ftable maybe can be coerced to parse the data, but I cannot
>>>> see
>>>> how after reading the documentation and experimenting with the
>>>> parameters.
>>>>
>>>> I'm using R 2.10.1 on osx 10.5.8 and 2.10.0 on Fedora 10.
>>>>
>>>> Any help/suggestions would be greatly appreciated. I can see that this
>>>> type
>>>> of issue is likely to grow in importance, and I'd also like to give the
>>>> data
>>>> owners suggestions on how to reformat their data so that it is easier to
>>>> consume by machines, while being easy to read for humans.
>>>>
>>>> The early records are a serious machine parsing challenge as they are
>>>> tiff
>>>> images of old notebooks ;-)
>>>>
>>>> tia
>>>>
>>>> Tim
>>>> Tim Coote
>>>> tim at coote.org
>>>> vincit veritas
>>>>
>>>> ______________________________________________
>>>> R-help at r-project.org mailing list
>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>> PLEASE do read the posting guide
>>>> http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>
>>>
>
> Tim Coote
> tim at coote.org
> vincit veritas
>
>
>
>