[R] strange behavior when reading csv - line wraps
Martin Tomko
martin.tomko at geo.uzh.ch
Sun May 31 12:06:01 CEST 2009
Dear Jim,
with the help of Ted, we diagnosed that the cause is in the extreme
variability in line length during reading in. As the table column number
is apparently determined fro mthe first five lines, what exceeds this
length gets automatically on the next line.
I am now trying to find a way to read in the data despite this. I have
no control over the table extent, the only thing that would make sense
according to my data would be to read in a fixed number of columns and
merge all remaining columns as a long string in the last one. No idea
how to do this, though.
Thanks
Martin
jim holtman wrote:
> It is still not clear to me exactly how you want to read the lines
> in. If the lines have a variable number of fields, and some of the
> lines might be wrapped, is there some way to determine where the start
> of each line is.
>
> If you are reading them in with read.csv, then the system is assuming
> that each line starts a new row. If this is not the case, then you
> will have to state the rules that determine where the lines start.
> You can always read the data in with 'scan' to separate each line and
> then do whatever processing is required to put together the rows in a
> data frame that you want.
>
> In one of your examples, you indicated that the line was split
> starting at the word "kempten"; if this is in the middle of the line,
> then you would have to create the break after reading the line in with
> 'scan' and then creating the rows in the dataframe. All of this can
> be done in R if you can state what the criteria is.
> On Sat, May 30, 2009 at 4:32 AM, Martin Tomko <martin.tomko at geo.uzh.ch
> <mailto:martin.tomko at geo.uzh.ch>> wrote:
>
> Jim,
> the two lines I put in are the actual problematic input lines.
> In these examples, there are no quotes nor # signs, although I
> have no means to make sure they do not occur in the inputs (any
> hints how I could deal with that?).
> I am trying to avoid as much pre-processing outside R as possible,
> and I have to process about 500 files with up to 3000 records
> each, so I need a more or less automated/batch solution. - so any
> string substitution will have to occur in R. But for the moment, I
> do not see a reaason for substitution, and the wrapping still occurs.
>
> Cheers
> Martin
>
>
>
> jim holtman wrote:
>
> You need to supply the actual input line so we can see what is
> happening. Are you sure you do not have unbalanced quotes in
> your input (try quote='') or do you have comment characters
> ("#") in your input?
>
> On Fri, May 29, 2009 at 3:15 PM, Martin Tomko
> <martin.tomko at geo.uzh.ch <mailto:martin.tomko at geo.uzh.ch>
> <mailto:martin.tomko at geo.uzh.ch
> <mailto:martin.tomko at geo.uzh.ch>>> wrote:
>
> Dear All,
> I am observing a strange behavior and searching the
> archives and
> help pages didn't help much.
> I have a csv with a variable number of fields in each line.
>
> I use
> dataPoints <- read.csv(inputFile, head=FALSE, sep=";",fill
> =TRUE);
>
> to read it in, and it works. But - some lines are long and
> 'wrap',
> or split and continue on the next line. So when I check the
> dim of
> the frame, they are not correct and I can see when I do a
> printout
> that the lines is split into two in the frame. I checked
> the input
> file and all is good.
>
> an example of the input is:
>
> 37;2175168475;13;8.522729;47.19537;16366682 at N00;30;sculpture;bird;tourism;animal;statue;canon;eos;rebel;schweiz;switzerland;eagle;swiss;adler;skulptur;zug;1750;28;tamron;f28;canton;tourismus;vogel;baar;kanton;xti;tamron1750;1750mm;tamron1750mm;400d;rabbitriotnet;
>
> where the last values occurs on the next line in the data
> frame.
>
> It does not have to be the last value, as in the follwong
> example,
> the word "kempten" starts the next line:
>
> 39;167757703;12;10.309295;47.724545;21903142 at N00;36;white;building;tower;clock;clouds;germany;bayern;deutschland;bavaria;europa;europe;eagle;adler;eu;wolke;dome;townhall;rathaus;turm;weiss;allemagne;europeanunion;bundesrepublik;gebaeude;glocke;brd;allgau;kuppel;europ;kempten;niemcy;europo;federalrepublic;europaischeunion;europaeischeunion;germanio;
>
> What could be the reason?
>
> I ws thinking about solving the issue by using a different
> separator, that I would use for the first 7 fields and
> concatenating all of the remaining values into a single stirng
> value, but could not figure out how to do such a
> substitution in
> R. Unfortunately, on my system I cannot specify a range for
> sed...
>
> Thanks for any help/pointers
> Martin
>
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>
> --
> Jim Holtman
> Cincinnati, OH
> +1 513 646 9390
>
> What is the problem that you are trying to solve?
>
>
>
>
>
> --
> Jim Holtman
> Cincinnati, OH
> +1 513 646 9390
>
> What is the problem that you are trying to solve?
--
Martin Tomko
Postdoctoral Research Assistant
Geographic Information Systems Division
Department of Geography
University of Zurich - Irchel
Winterthurerstr. 190
CH-8057 Zurich, Switzerland
email: martin.tomko at geo.uzh.ch
site: http://www.geo.uzh.ch/~mtomko
mob: +41-788 629 558
tel: +41-44-6355256
fax: +41-44-6356848
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