Ahh ..
On Jul 27, 2009, at 6:01 PM, Mehdi Khan wrote:
Even when choosing a value from the first few rows, it doesn't work.
okay here it goes:
> rearranged[1:10, 1:5]
x y band1 VSCAT.001 soiltype
1 -124.3949 40.42468 NA NA CD
2 -124.3463 40.27358 NA NA CD
3 -124.3357 40.25226 NA NA CD
4 -124.3663 40.40241 NA NA CD
5 -124.3674 40.49810 NA NA CD
6 -124.3083 40.24744 NA 464 <NA>
7 -124.3017 40.31295 NA NA D
8 -124.3375 40.47557 NA 464 <NA>
9 -124.2511 40.11697 1 NA <NA>
10 -124.2532 40.12640 1 NA <NA>
> query<- rearranged$y== 40.42468
> rearranged[query,]
[1] x y band1 VSCAT.001 soiltype
<0 rows> (or 0-length row.names)
This isn't working because the numbers you see for y (40.42468) isn't
precisely what that number is. As I mentioned before you should use an
"almost.equals" type of search for this scenario. My "%~%" function
isn't working in your session because that is a function I've defined
myself. You can of course use it, you just have to define it in your
workspace. Paste these lines into your workspace (or save them to a
file and "source" that file into your workspace).
## === almost.equal functions ====
almost.equal <- function(x, y, tolerance=.Machine$double.eps^0.5) {
abs(x - y) < tolerance
}
"%~%" <- function(x, y) almost.equal(x, y)
## === end paste ==============
Now you can use %~% once that's in. Let's use the almost.equal
function now because I don't know if the default tolerance here is too
strict (I suspect showing the value for rearranged$y[1] will show you
more significant digits than you're seeing in the table(?))
query <- almost.equal(rearranged$y, 40.42468, tolerance=0.0001)
rearranged[query,]
This will get you something.
query<- rearranged$ VSCAT.001== 464
except it's a huge table (I guess I have to get rid of all rows
with NA).
Yes, I believe I mentioned earlier that you have to axe the NA matches
manually:
query <- rearranged$VSCAT.001 == 464 & !is.na(rearranged$VSCAT.001)
rearranged[query,]
Will get you what you want.
I tried using the %~% but R doesn't recognize it. So maybe it has
to do with the rounding errors?
Rounding errors won't happen with integer comparisons (and it looks
like the VSCAT.001 columns is integers, no?).
-steve
--
Steve Lianoglou
Graduate Student: Computational Systems Biology
| Memorial Sloan-Kettering Cancer Center
| Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact
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