thank you VERY much, I have to run now, but I will look at this in the next
few days (going on a field trip). I really appreciate it!
Mehdi Khan
On Tue, Jul 21, 2009 at 12:49 PM, Steve Lianoglou <
mailinglist.honey...@gmail.com> wrote:
>
> On Jul 21, 2009, at 3:27 PM, Mehdi Khan wrote:
>
> I understand your explanation about the test for even numbers. However I
>> am still a bit confused as to how to go about finding a particular value.
>> Here is an example data set
>>
>> col # attr1 attr2 attr 3 LON LAT
>> 17209 D NA NA -122.9409 38.27645
>> 17210 BC NA NA -122.9581 38.36304
>> 17211 B NA NA -123.6851 41.67121
>> 17212 BC NA NA -123.0724 38.93073
>> 17213 C NA NA -123.7240 41.84403
>> 17214 <NA> 464 NA -122.9430 38.30988
>> 17215 C NA NA -123.4442 40.65369
>> 17216 BC NA NA -122.9389 38.31551
>> 17217 C NA NA -123.0747 38.97998
>> 17218 C NA NA -123.6580 41.59610
>> 17219 C NA NA -123.4513 40.70992
>> 17220 C NA NA -123.0901 39.06473
>> 17221 BC NA NA -123.0653 38.94845
>> 17222 BC NA NA -122.9464 38.36808
>> 17223 <NA> 464 NA -123.0143 38.70205
>> 17224 <NA> NA 5 -122.8609 37.94137
>> 17225 <NA> NA 5 -122.8628 37.95057
>> 17226 <NA> NA 7 -122.8646 37.95978
>>
>
> For future reference, perhaps paste this in a way that's easy for us to
> paste into a running R session so we can use it, like so:
>
> df <- data.frame(
> coln=c(17209, 17210, 17211, 17212, 17213, 17214, 17215, 17216, 17217,
> 17218, 17219, 17220, 17221, 17222, 17223, 17224, 17225, 17226),
>
> attr1=c("D","BC","B","BC","C",NA,"C","BC","C","C","C","C","BC","BC",NA,NA,NA,NA),
> attr2=c( NA,NA,NA,NA,NA,464,NA,NA,NA,NA,NA,NA,NA,NA,464,NA,NA,NA),
> attr3=c(NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,NA,5,5,7),
> LON=c(
> -122.9409,-122.9581,-123.6851,-123.0724,-123.7240,-122.9430,-123.4442,-122.9389,-123.0747,-123.6580,-123.4513,-123.0901,-123.0653,-122.9464,-123.0143,-122.8609,-122.8628,-122.8646),
>
> LAT=c(38.27645,38.36304,41.67121,38.93073,41.84403,38.30988,40.65369,38.31551,38.97998,41.59610,40.70992,39.06473,38.94845,38.36808,38.70205,37.94137,37.95057,37.95978))
>
> If I wanted to find the row with Lat = 37.95978
>>
>
> Using an "indexing vector":
>
> R> lats <- df$LAT == 37.95978
> # or with the %~% from before:
> # lats <- df$LAT %~% 37.95978
> R> df[lats,]
> coln attr1 attr2 attr3 LON LAT
> 18 17226 <NA> NA 7 -122.8646 37.95978
>
> Using the "subset" function:
>
> R> subset(df, LAT == 37.95978)
> coln attr1 attr2 attr3 LON LAT
> 18 17226 <NA> NA 7 -122.8646 37.95978
>
> , how would i do that? How would I find the rows with BC?
>>
>
> R> subset(df, attr1 == 'BC')
> coln attr1 attr2 attr3 LON LAT
> 2 17210 BC NA NA -122.9581 38.36304
> 4 17212 BC NA NA -123.0724 38.93073
> 8 17216 BC NA NA -122.9389 38.31551
> 13 17221 BC NA NA -123.0653 38.94845
> 14 17222 BC NA NA -122.9464 38.36808
>
>
> If you try with an "indexing vector" the NA's will trip you up:
>
> R> df[df$attr1 == 'BC',]
> coln attr1 attr2 attr3 LON LAT
> 2 17210 BC NA NA -122.9581 38.36304
> 4 17212 BC NA NA -123.0724 38.93073
> NA NA <NA> NA NA NA NA
> 8 17216 BC NA NA -122.9389 38.31551
> 13 17221 BC NA NA -123.0653 38.94845
> 14 17222 BC NA NA -122.9464 38.36808
> NA.1 NA <NA> NA NA NA NA
> NA.2 NA <NA> NA NA NA NA
> NA.3 NA <NA> NA NA NA NA
> NA.4 NA <NA> NA NA NA NA
>
> So you could do something like:
>
> > df[df$attr1 == 'BC' & !is.na(df$attr1),]
> coln attr1 attr2 attr3 LON LAT
> 2 17210 BC NA NA -122.9581 38.36304
> 4 17212 BC NA NA -123.0724 38.93073
> 8 17216 BC NA NA -122.9389 38.31551
> 13 17221 BC NA NA -123.0653 38.94845
> 14 17222 BC NA NA -122.9464 38.36808
>
>
> HTH,
> -steve
>
> --
> Steve Lianoglou
> Graduate Student: Physiology, Biophysics and Systems Biology
> Weill Medical College of Cornell University
>
> Contact Info:
> http://cbio.mskcc.org/~lianos/contact<http://cbio.mskcc.org/%7Elianos/contact>
>
>
>
>
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