bug in process definition for retrieving point pair indexes from varigramCloud

Does .BigInt always exist and always contain the appropriate divisor 
regardless of the architecture?  If not, does it exist _only_ for 
64-bit architectures?

Is the result of the operation always an offset, regardless of the 
architecture?  (I am presuming yes, but I don't have access to a 
32-bit machine right now).

If I am writing R code to extract left and right appropriately, I'd 
like to make sure it is portable across architectures.  I am presuming 
that this is the best way to get left and right.  Capturing the 
results of print(variogramCloud) seems kludgy.
Better method than both of these available?

On 02/28/2010 10:37 AM, Edzer Pebesma wrote:

Well, they're called first and second, and a bit later they're named 
"left" and "right", it nowhere says that "left" is first, or second.

As you say, there's little point in making the distinction anyway; 
give me a case where it is confusing and I'll change it.
-- 
Edzer

Mark Connolly wrote:

Thanks.  That works better.

It looks as though the documentation has left and right (implicitly) 
switched?  I am drawing line segments in 3D space using rgl, and I 
don't care so much about the order.  Might be confusing in some cases.


On 02/28/2010 09:49 AM, Edzer Pebesma wrote:

Mark, the documentation falsely assumes all computers have 32 bits 
integers; yours seems not -- compare the .BigInt with sqrt(2^64). 
To see how the point pairs are obtained, look at:

gstat:::as.data.frame.variogramCloud

function (x, row.names, optional, ...)
{
   .BigInt = attr(x, ".BigInt")
   x$left = x$np%%.BigInt + 1
   x$right = x$np%/%.BigInt + 1
   x$np = NULL
   class(x) = "data.frame"
   x
}

so the .BigInt attribute is the divisor; 1 is added because the 
arrays are set up in the C code, starting at 0.
-- 
Edzer

Mark Connolly wrote:

gstat reference states

If cloud is TRUE: an object of class variogramCloud, with the 
field np encoding the numbers of the point pair that contributed 
to a variogram cloud estimate, as follows. The first point is 
found by the integer division of np by 2^16, the second point by 
the remainder of that division.

For
Classes ?variogramCloud? and 'data.frame': 3275 obs. of 6 variables:
$ np : num 8.59e+09 8.00 8.59e+09 1.29e+10 1.29e+10 ...
$ dist : num 18.8 79.2 77.8 78.7 100.1 ...
$ gamma : num 0.781 0.845 12.903 5.611 0.344 ...
$ dir.hor: num 0 0 0 0 0 0 0 0 0 0 ...
$ dir.ver: num 0 0 0 0 0 0 0 0 0 0 ...
$ id : Factor w/ 1 level "var1": 1 1 1 1 1 1 1 1 1 1 ...
- attr(*, "direct")='data.frame': 1 obs. of 2 variables:
..$ id : Factor w/ 1 level "var1": 1
..$ is.direct: logi TRUE
- attr(*, ".BigInt")= num 4.29e+09


v[1,] yields:
dist gamma dir.hor dir.ver id left right
1 18.75474 0.78125 0 0 var1 6 3


v$np[1] %/% 2^16 yields:
131072

Which is != 6

Am I misinterpreting the documentation?