Question about Calculation of Cross Product

An embedded and charset-unspecified text was scrubbed...
Name: not available
URL: <https://stat.ethz.ch/pipermail/r-help/attachments/20111103/221198de/attachment.pl>
Try

library(pracma)
? cross

Michael Weylandt
The function of crossprod in R puzzled me.
I would like to calculate the cross product of two vectors. According to my text book, it defines like this:
a = (ax, ay, az)
b = (bx, by, bz)
then, the cross product of a and b is:
a X b = (ay*bz-az*by, az*bx-ax*bz, ax*by-ay*bz)
It can also write in a determinant format.

But the crossprod or tcrossprod function in R appeared not calculate the cross product. Suppose I enter this:
a = c(1, 2, 3)
b = c(2, 3, 4)
ab = crossprod(a, b)
ab
? ? [,1]
[1,] ? 20
ab = tcrossprod(a, b)
ab
? ? [,1] [,2] [,3]
[1,] ? ?2 ? ?3 ? ?4
[2,] ? ?4 ? ?6 ? ?8
[3,] ? ?6 ? ?9 ? 12

Does any know how to calculate cross product in R. Or I have to write the function myself?
? ? ? ?[[alternative HTML version deleted]]

______________________________________________
R-help at 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.

An embedded and charset-unspecified text was scrubbed...
Name: not available
URL: <https://stat.ethz.ch/pipermail/r-help/attachments/20111103/f5ac65b2/attachment.pl>
The crossprod function in base R implements the MATRIX cross product, more familiarly known as "matrix multiplication".
The term "crossprod" is thereby rather misleading, nicht wahr?

Wouldn't it be *nice* to put into the help file a wee warning telling
the young naive user (explicitly) that this is *not* the "usual" 3-D
vector cross product? :-)

     cheers,

         Rolf Turner