R help - Jul 2001 - vector angle

Hi everyone,


I'm translating into R some programs I worked through in Matlab to
calculate the angle between two vectors (very large--like 6200 rows in
each vector).  In Matlab, I used a series of nested for loops, because I
was calculating the angles between many pairs of vectors.  I know for
loops are not desirable in R code, so I was wondering if anyone could
recommend a faster way to complete this task.  Also, I have NAs in my
vectors--I've had trouble performing various operations on my vectors in R
because of these NAs.

Any advice on this would be greatly appreciated.

Thanks!
Evan Macosko


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Evan Zane Macosko wrote:
> Hi everyone,
>
> I'm translating into R some programs I worked through in Matlab to
> calculate the angle between two vectors (very large--like 6200 rows in
> each vector).  In Matlab, I used a series of nested for loops, because I
> was calculating the angles between many pairs of vectors.  I know for
> loops are not desirable in R code, so I was wondering if anyone could
> recommend a faster way to complete this task.  Also, I have NAs in my
> vectors--I've had trouble performing various operations on my vectors
in R
> because of these NAs.
>
> Any advice on this would be greatly appreciated.
As far as I know, the use of apply (sapply and lapply) would make things run
faster than 'for' loops.


About the NAs, you may want to ignore the vectors which have a NA coordinate, or
may be do something else...
to have a foot in this, you may try the help for the functions 'is.na'
and
'na.action'.



I hope it helps,




Laurent



--
Laurent Gautier                 CBS, Building 208, DTU
PhD. Student                    D-2800 Lyngby,Denmark
tel: +45 45 25 24 85            http://www.cbs.dtu.dk/laurent


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