Thank you - it is refreshing to have a helpful answer.  I am glad some
people remember the days when they were first learning too.



On Thu, May 12, 2011 at 4:58 PM, jlemaitre [via R] <
ml-node+3518836-766936252-236833@n4.nabble.com> wrote:

> Nielsen,
> The numbers in the brackets reference a component of a matrix/data
> frame/vector. So if you have:
> > x <- c(1:10) # a vector of integers in sequence from 1-10
> > x[3] # the third component of x
> [1] 3
>
> For 2-way matrices or data frames, the formatting is [row,column]. So, for
> a 10 x 10 matrix x:
> > x <- matrix(1:100, ncol = 10, byrow = T)
> > x
>       [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
>  [1,]    1    2    3    4    5    6    7    8    9    10
>  [2,]   11   12   13   14   15   16   17   18   19    20
>  [3,]   21   22   23   24   25   26   27   28   29    30
>  [4,]   31   32   33   34   35   36   37   38   39    40
>  [5,]   41   42   43   44   45   46   47   48   49    50
>  [6,]   51   52   53   54   55   56   57   58   59    60
>  [7,]   61   62   63   64   65   66   67   68   69    70
>  [8,]   71   72   73   74   75   76   77   78   79    80
>  [9,]   81   82   83   84   85   86   87   88   89    90
> [10,]   91   92   93   94   95   96   97   98   99   100
>
> > x[,1] # return the first column of x
>  [1]  1 11 21 31 41 51 61 71 81 91
>
> > x[1,] # return the first row of x
>  [1]  1  2  3  4  5  6  7  8  9 10
>
> when there's a minus, it just means that component is omitted
>
> > x[-1,] # return x less the first row
>       [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
>  [1,]   11   12   13   14   15   16   17   18   19    20
>  [2,]   21   22   23   24   25   26   27   28   29    30
>  [3,]   31   32   33   34   35   36   37   38   39    40
>  [4,]   41   42   43   44   45   46   47   48   49    50
>  [5,]   51   52   53   54   55   56   57   58   59    60
>  [6,]   61   62   63   64   65   66   67   68   69    70
>  [7,]   71   72   73   74   75   76   77   78   79    80
>  [8,]   81   82   83   84   85   86   87   88   89    90
>  [9,]   91   92   93   94   95   96   97   98   99   100
>
> Given this context, I would double check the contents of test vs. test1.
> And don't let arrogant posts on this help forum discourage you.
> I hope this helps.
>
>
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>



-- 
Lindsey Nielsen, Ph.D.
Los Alamos National Lab
(505) 667-2835


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