[R] R data query

[Marc Schwartz]

On Thu, 2006-09-21 at 13:07 +0100, Al-Kharusi, L. wrote:
> Dear Sir/Madam,
> 
> 
> I am encountering one of those alien computer momements one finds every
> so often in life. See the sequence below:
> 
> > fish3.fis <-read.csv("emperor2.csv", check.names = TRUE, strip.white =
> TRUE)
> > colnames(fish3.fis)
>  [1] "Month"           "Year"            "FishingArea"
> "SumOfTotalCatch" "CPUE"           
>  [6] "rCPUE"           "PA"              "Latitude"        "Longitude"
> "Depth"          
> [11] "SST"            
> > hist(CPUE)
> Error in hist(CPUE) : Object "CPUE" not found
> 
> So, the system knows CPUE exists, but will not do a hist or a gam model
> using the term - but for some strange reason it will do a plot. I have
> created a completely different data file and that same problem is
> happening. The imported files are exactly the same as I was using quite
> happily last month. 
> 
> As you will see from the above I've tried adding check.names and
> strip.white in the reading in process to avoid the unseen effect of
> blank spaces.
> 
> Any ideas what I might do next? Have you come across this issue at all? 
> 
> Thanks

CPUE is not found, as it is a column within the R data frame object
fish3.fis.

There are (at least) 5 ways to do a histogram on CPUE:

1.  attach() the data frame, which puts it in the search path and you
can then use the column name alone:

  attach(fish3.fis)
  hist(CPUE)
  detach(fish3.fis)

2. Identify the column using the '$' function:

  hist(fish3.fis$CPUE)

3. Use with() to evaluate the hist() call within the environment of the
data frame:

  with(fish3.fis, hist(CPUE))

4. Use the "[" function:

  hist(fish3.fis[, "CPUE"])

5. Use the "[[" function:

  hist(fish3.fis[["CPUE"]])


This is covered in "An Introduction to R".

HTH,

Marc Schwartz