[R-SIG-Finance] Index of data is missing (dim is NULL)

[Joshua Ulrich]

Please use this list for finance-related questions.  Just because
you're using R to solve a finance-related problem does not mean your
question is finance-related.

In this case, your "problem" is that rel_data is a *vector*.  Please
read, "An Introduction to R" to understand the differences between
vectors and matrices / data.frames (and note that subsetting a matrix
via "[" with drop=TRUE can result in a vector).

> x <- 1:10  # This is a vector
> dim(x)
NULL
> x[1,]
Error in x[1, ] : incorrect number of dimensions
> matrix(1:10,2)  # This is a matrix
     [,1] [,2] [,3] [,4] [,5]
[1,]    1    3    5    7    9
[2,]    2    4    6    8   10
> matrix(1:10,2)[1,]  # This is a vector
[1] 1 3 5 7 9
> matrix(1:10,2)[1,,drop=FALSE]  # This is a matrix
     [,1] [,2] [,3] [,4] [,5]
[1,]    1    3    5    7    9


HTH,
Josh
--
http://www.fosstrading.com



On Wed, Sep 2, 2009 at 6:26 AM, sunil<sarswat at gmail.com> wrote:
> Hi Users,
>             I am working on F&O order-book data, and I noticed index of
> subset of data is missing? Usually when you type the variable name it shows
> you row numbers like [1,], [2,] etc., but here row number is missing. When I
> ask for dim(data) command , it shows "NULL" ? Please see below
>
>> rel_data
>       symbols insuments_type    expire date       quantity          price
>  time_stamp             BS     order_type
>  "JPASSOCIAT"       "FUTSTK"     "20080424"          "750"       "240.90"
>  "13:55:30"            "S"           "RL"
>> dim(rel_data)
> NULL
>> rel_data[1,]
> Error in rel_data[1, ] : incorrect number of dimensions
>>
>
>