R help - Nov 2011 - Named rows in a table (data frame) read from a file

I read a table as follows:
> F1 <- read.table("Rtext3.txt")
> F1
  Price Floor Area Rooms Age Cent.heat
a 52.00   111  830     5 6.2        no
b 54.75   128  710     5 7.5        no
c 57.50   101 1000     5 4.2        no
d 57.50   131  690     6 8.8        no
e 59.75    93  900     5 1.9       yes

As it is seen, the rows have a name. However I don't know how to access a 
particular element from that name, for instance,
> attach(F1)
> Price
[1] 52.00 54.75 57.50 57.50 59.75
> Price[["a"]]
Error en Price[["a"]] : sub?ndice fuera de  los
l?mites
> Price$a
Error en Price$a : $ operator is invalid for atomic
vectors
> Price['a']
[1] NA
> Price["a"]
[1] NA

If I cannot access particular elements of the frame components by the row names,
is there any use of having the rows named?

Thanks,

Sergio.

Don't use attach. I know it's tempting, but it's really not worth it
in the long run.  (Cf. Genesis 3, ff.)

This works:

F1["a", "Price"]

Incidentally the reason yours didn't work is because the row names are part
of F1, not Price so attach() doesn't carry them along.

In short, row names good; attach bad. 

Michael


On Nov 16, 2011, at 7:11 PM, JulioSergio <juliosergio at gmail.com> wrote:
> I read a table as follows:
> 
>> F1 <- read.table("Rtext3.txt")
>> F1
>  Price Floor Area Rooms Age Cent.heat
> a 52.00   111  830     5 6.2        no
> b 54.75   128  710     5 7.5        no
> c 57.50   101 1000     5 4.2        no
> d 57.50   131  690     6 8.8        no
> e 59.75    93  900     5 1.9       yes
> 
> As it is seen, the rows have a name. However I don't know how to access
a
> particular element from that name, for instance,
> 
>> attach(F1)
>> Price
> [1] 52.00 54.75 57.50 57.50 59.75
>> Price[["a"]]
> Error en Price[["a"]] : sub?ndice fuera de  los l?mites
>> Price$a
> Error en Price$a : $ operator is invalid for atomic vectors
>> Price['a']
> [1] NA
>> Price["a"]
> [1] NA
> 
> If I cannot access particular elements of the frame components by the row
names,
> is there any use of having the rows named?
> 
> Thanks,
> 
> Sergio.
> 
> ______________________________________________
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Hi,

On Wed, Nov 16, 2011 at 7:11 PM, JulioSergio <juliosergio at gmail.com>
wrote:
> I read a table as follows:
>
>> F1 <- read.table("Rtext3.txt")
>> F1
> ?Price Floor Area Rooms Age Cent.heat
> a 52.00 ? 111 ?830 ? ? 5 6.2 ? ? ? ?no
> b 54.75 ? 128 ?710 ? ? 5 7.5 ? ? ? ?no
> c 57.50 ? 101 1000 ? ? 5 4.2 ? ? ? ?no
> d 57.50 ? 131 ?690 ? ? 6 8.8 ? ? ? ?no
> e 59.75 ? ?93 ?900 ? ? 5 1.9 ? ? ? yes
>
> As it is seen, the rows have a name. However I don't know how to access
a
> particular element from that name, for instance,
>
>> attach(F1)
That's your biggest problem. Don't attach your dataframe.
>> Price
> [1] 52.00 54.75 57.50 57.50 59.75
>> Price[["a"]]
> Error en Price[["a"]] : sub?ndice fuera de ?los l?mites
>> Price$a
> Error en Price$a : $ operator is invalid for atomic vectors
>> Price['a']
> [1] NA
>> Price["a"]
> [1] NA
>
> If I cannot access particular elements of the frame components by the row
names,
> is there any use of having the rows named?
Sure you can. It works just like any other indexing of data frames,
with the caveat that a data frame is really a list with the columns as
elements, so there are indexing options not available for rows.

Since you didn't provide any data, here's a toy example:
> test <- data.frame(X=1:3, Y=4:6, Z=7:9)
> rownames(test) <- c("a", "b", "c")
> test
  X Y Z
a 1 4 7
b 2 5 8
c 3 6 9
> test["a",]
  X Y Z
a 1 4 7
> test["a", "Y"]
[1] 4
> test["a",][3]
  Z
a 7

Sarah
> Thanks,
>
> Sergio.
>

-- 
Sarah Goslee
http://www.functionaldiversity.org

R. Michael Weylandt <michael.weylandt <at> gmail.com>
<michael.weylandt <at>
gmail.com> writes:
..

Thanks Michael