[R] About 5.1 Arrays
Stephen Liu
satimis at yahoo.com
Fri Nov 5 09:22:39 CET 2010
Hi folks,
(Learning R)
5.1 Arrays
http://cran.r-project.org/doc/manuals/R-intro.html#Vectors-and-assignment
1)
If continued on previous example (3.1 Intrinsic attributes: mode and length),
> z <- 0:9
> dim(z) <- c(3,5,100)
Error in dim(z) <- c(3, 5, 100) :
dims [product 1500] do not match the length of object [10]
failed.
2)
Ran;
> z <- 0:1499
> dim(z) <- c(3,5,100)
> dim(z)
[1] 3 5 100
It worked
OR
3)
> z <- 1:1500
> dim(z) <- c(3,5,100)
> dim(z)
[1] 3 5 100
It also worked.
> z
[1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14
[15] 15 16 17 18 19 20 21 22 23 24 25 26 27 28
.....
[1485] 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498
[1499] 1499 1500
"0" is counted as 1 object.
Does "object length" mean the total number of objects/entries?
Please help me to understand follow;
"For example if the dimension vector for an array, say a, is c(3,4,2) then there
are 3 * 4 * 2 = 24 entries in a and the data vector holds them in the order
a[1,1,1], a[2,1,1], ..., a[2,4,2], a[3,4,2]."
I don't understand;
a[1,1,1], a[2,1,1], ..., a[2,4,2]
1 * 1 * 1 / 2 * 1 * 1 / 2 * 4 * 2 is NOT 24 ?
TIA
B.R.
Stephen L
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