Is this something like what you were asking for? The output of a
'split' will be a list of the dataframe subsets for the categories you
have specified.
> x <- data.frame(g1=sample(LETTERS[1:2],30,TRUE),
+ g2=sample(letters[1:2], 30, TRUE),
+ g3=1:30)
> y <- split(x, list(x$g1, x$g2))
> str(y)
List of 4
$ A.a:'data.frame': 7 obs. of 3 variables:
..$ g1: Factor w/ 2 levels "A","B": 1 1 1 1 1 1 1
..$ g2: Factor w/ 2 levels "a","b": 1 1 1 1 1 1 1
..$ g3: int [1:7] 3 4 6 8 9 13 24
$ B.a:'data.frame': 7 obs. of 3 variables:
..$ g1: Factor w/ 2 levels "A","B": 2 2 2 2 2 2 2
..$ g2: Factor w/ 2 levels "a","b": 1 1 1 1 1 1 1
..$ g3: int [1:7] 10 11 16 17 18 20 25
$ A.b:'data.frame': 6 obs. of 3 variables:
..$ g1: Factor w/ 2 levels "A","B": 1 1 1 1 1 1
..$ g2: Factor w/ 2 levels "a","b": 2 2 2 2 2 2
..$ g3: int [1:6] 2 12 23 26 27 29
$ B.b:'data.frame': 10 obs. of 3 variables:
..$ g1: Factor w/ 2 levels "A","B": 2 2 2 2 2 2 2 2 2 2
..$ g2: Factor w/ 2 levels "a","b": 2 2 2 2 2 2 2 2 2 2
..$ g3: int [1:10] 1 5 7 14 15 19 21 22 28 30
> y
$A.a
g1 g2 g3
3 A a 3
4 A a 4
6 A a 6
8 A a 8
9 A a 9
13 A a 13
24 A a 24
$B.a
g1 g2 g3
10 B a 10
11 B a 11
16 B a 16
17 B a 17
18 B a 18
20 B a 20
25 B a 25
$A.b
g1 g2 g3
2 A b 2
12 A b 12
23 A b 23
26 A b 26
27 A b 27
29 A b 29
$B.b
g1 g2 g3
1 B b 1
5 B b 5
7 B b 7
14 B b 14
15 B b 15
19 B b 19
21 B b 21
22 B b 22
28 B b 28
30 B b 30
> y[[2]]
g1 g2 g3
10 B a 10
11 B a 11
16 B a 16
17 B a 17
18 B a 18
20 B a 20
25 B a 25
>
>
>
On Sat, Jul 12, 2008 at 8:51 PM, <[EMAIL PROTECTED]> wrote:
> OK. Now I know that I am dealing with a data frame. One last question on this
> topic. a <- read.csv() gives me a dataframe. If I have 'c <- split(x,
> x$Category), then what is returned by split in this case? c[1] seems to be
> OK but c[2] is not right in my mind. If I run ci <- split(nrow(a),
> a$Category). And then ci[1] seems to be the rows associated with the first
> category, c[2] is the indices/rows associated with the second category, etc.
> But this seems different than c[1], c[2], etc.
>
> Using the techniques below I can get the information on the categories. Now
> as an extra level of complexity there are SubCategories within each Category.
> Assume that the SubCategory names are not unique within the dataset so if I
> want the SubCategory data I need to retrive the indices (or data) for the
> Category and SubCategory pair. In other words if I have a Category that
> ranges from 'A' to 'Z', it is possible that I might have a subcategory A a, A
> b (where a and b are the sub category names). I also might have B a, B b. I
> want all of the sub categories A a. NOT the subcategories a (because that
> might include B a which would be different). I am guessing that this will
> take more than a simple 'split'.
>
> Thank you.
>
> Kevin
>
> ---- Duncan Murdoch <[EMAIL PROTECTED]> wrote:
>> On 12/07/2008 3:59 PM, [EMAIL PROTECTED] wrote:
>> > I am sorry but if read.csv returns a dataframe and a dataframe is like a
>> > matrix and I have a set of input like below and a[1,] gives me the first
>> > row, what is the second index? From what I read and your input I am
>> > guessing that it is the column number. So a[1,1] would return the
>> > DayOfYear column for the first row, right? What does a$DayOfYear return?
>>
>> a$DayOfYear would be the same as a[,1] or a[,"DayOfYear"], i.e. it would
>> return the entire first column.
>>
>> Duncan Murdoch
>>
>> >
>> > Thank you for your patience.
>> >
>> > Kevin
>> >
>> > ---- Duncan Murdoch <[EMAIL PROTECTED]> wrote:
>> >> On 12/07/2008 12:31 PM, [EMAIL PROTECTED] wrote:
>> >>> I am using a simple R statement to read in the file:
>> >>>
>> >>> a <- read.csv("Sample.dat", header=TRUE)
>> >>>
>> >>> There is alot of data but the first few lines look like:
>> >>>
>> >>> DayOfYear,Quantity,Fraction,Category,SubCategory
>> >>> 1,82,0.0000390392720794458,(Unknown),(Unknown)
>> >>> 2,78,0.0000371349173438631,(Unknown),(Unknown)
>> >>> . . .
>> >>> 71,2,0.0000009521773677913,WOMEN,Piratesses
>> >>> 72,4,0.0000019043547355827,WOMEN,Piratesses
>> >>> 73,3,0.0000014282660516870,WOMEN,Piratesses
>> >>> 74,14,0.0000066652415745395,WOMEN,Piratesses
>> >>> 75,2,0.0000009521773677913,WOMEN,Piratesses
>> >>>
>> >>> If I read the data in as above, the command
>> >>>
>> >>> a[1]
>> >>>
>> >>> results in the output
>> >>>
>> >>> [ reached getOption("max.print") -- omitted 16193 rows ]]
>> >>>
>> >>> Shouldn't this be the first row?
>> >> No, the first row would be a[1,]. read.csv() returns a dataframe, and
>> >> those are indexed with two indices to treat them like a matrix, or with
>> >> one index to treat them like a list of their columns.
>> >>
>> >> Duncan Murdoch
>> >>
>> >>> a$Category[1]
>> >>>
>> >>> results in the output
>> >>>
>> >>> [1] (Unknown)
>> >>> 4464 Levels: Tags ... WOMEN
>> >>>
>> >>> But
>> >>>
>> >>> a$Category[365]
>> >>>
>> >>> gives me:
>> >>>
>> >>> [1] 7 Plates (Dessert),Western\n120,5,0.0000023804434194784,7 Plates
>> >>> (Dessert)
>> >>> 4464 Levels: Tags ... WOMEN
>> >>>
>> >>> There is something fundamental about either vectors of the read.csv
>> >>> command that I am missing here.
>> >>>
>> >>> Thank you.
>> >>>
>> >>> Kevin
>> >>>
>> >>> ---- jim holtman <[EMAIL PROTECTED]> wrote:
>> >>>> Please provide commented, minimal, self-contained, reproducible code,
>> >>>> or at least a before/after of what you data would look like. Taking a
>> >>>> guess at what you are asking, here is one way of doing it:
>> >>>>
>> >>>>
>> >>>>> x <- data.frame(cat=sample(LETTERS[1:3],20,TRUE),a=1:20, b=runif(20))
>> >>>>> x
>> >>>> cat a b
>> >>>> 1 B 1 0.65472393
>> >>>> 2 C 2 0.35319727
>> >>>> 3 B 3 0.27026015
>> >>>> 4 A 4 0.99268406
>> >>>> 5 C 5 0.63349326
>> >>>> 6 A 6 0.21320814
>> >>>> 7 C 7 0.12937235
>> >>>> 8 A 8 0.47811803
>> >>>> 9 A 9 0.92407447
>> >>>> 10 A 10 0.59876097
>> >>>> 11 A 11 0.97617069
>> >>>> 12 A 12 0.73179251
>> >>>> 13 B 13 0.35672691
>> >>>> 14 C 14 0.43147369
>> >>>> 15 C 15 0.14821156
>> >>>> 16 C 16 0.01307758
>> >>>> 17 B 17 0.71556607
>> >>>> 18 B 18 0.10318424
>> >>>> 19 C 19 0.44628435
>> >>>> 20 B 20 0.64010105
>> >>>>> # create a list of the indices of the data grouped by 'cat'
>> >>>>> split(seq(nrow(x)), x$cat)
>> >>>> $A
>> >>>> [1] 4 6 8 9 10 11 12
>> >>>>
>> >>>> $B
>> >>>> [1] 1 3 13 17 18 20
>> >>>>
>> >>>> $C
>> >>>> [1] 2 5 7 14 15 16 19
>> >>>>
>> >>>>> # or do you want the data
>> >>>>> split(x, x$cat)
>> >>>> $A
>> >>>> cat a b
>> >>>> 4 A 4 0.9926841
>> >>>> 6 A 6 0.2132081
>> >>>> 8 A 8 0.4781180
>> >>>> 9 A 9 0.9240745
>> >>>> 10 A 10 0.5987610
>> >>>> 11 A 11 0.9761707
>> >>>> 12 A 12 0.7317925
>> >>>>
>> >>>> $B
>> >>>> cat a b
>> >>>> 1 B 1 0.6547239
>> >>>> 3 B 3 0.2702601
>> >>>> 13 B 13 0.3567269
>> >>>> 17 B 17 0.7155661
>> >>>> 18 B 18 0.1031842
>> >>>> 20 B 20 0.6401010
>> >>>>
>> >>>> $C
>> >>>> cat a b
>> >>>> 2 C 2 0.35319727
>> >>>> 5 C 5 0.63349326
>> >>>> 7 C 7 0.12937235
>> >>>> 14 C 14 0.43147369
>> >>>> 15 C 15 0.14821156
>> >>>> 16 C 16 0.01307758
>> >>>> 19 C 19 0.44628435
>> >>>>
>> >>>>
>> >>>> On Sat, Jul 12, 2008 at 3:32 AM, <[EMAIL PROTECTED]> wrote:
>> >>>>> I have search the archive and I could not find what I need so I will
>> >>>>> try to ask the question here.
>> >>>>>
>> >>>>> I read a table in (read.table)
>> >>>>>
>> >>>>> a <- read.table(.....)
>> >>>>>
>> >>>>> The table has column names like DayOfYear, Quantity, and Category.
>> >>>>>
>> >>>>> The values in the row for Category are strings (characters).
>> >>>>>
>> >>>>> I want to get all of the rows grouped by Category. The number of
>> >>>>> unique category names could be around 50. Say for argument sake the
>> >>>>> number of categories is exactly 50. Can I somehow get a vector of
>> >>>>> length 50 containing the rows corresponding to the category (another
>> >>>>> vector)? I realize I can access any row a[i]$Category (right?). But I
>> >>>>> wanta vector containing the rows corresponding to each distinct
>> >>>>> Category name.
>> >>>>>
>> >>>>> Thank you.
>> >>>>>
>> >>>>> Kevin
>> >>>>>
>> >>>>> ______________________________________________
>> >>>>> R-help@r-project.org mailing list
>> >>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>> >>>>> PLEASE do read the posting guide
>> >>>>> http://www.R-project.org/posting-guide.html
>> >>>>> and provide commented, minimal, self-contained, reproducible code.
>> >>>>>
>> >>>>
>> >>>> --
>> >>>> Jim Holtman
>> >>>> Cincinnati, OH
>> >>>> +1 513 646 9390
>> >>>>
>> >>>> What is the problem you are trying to solve?
>> >>> ______________________________________________
>> >>> R-help@r-project.org mailing list
>> >>> https://stat.ethz.ch/mailman/listinfo/r-help
>> >>> PLEASE do read the posting guide
>> >>> http://www.R-project.org/posting-guide.html
>> >>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem you are trying to solve?
______________________________________________
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