[R] [FORGED] Re: help with r package "trip"

[Michael Sumner]

On Wed, 15 Jun 2016 at 18:51 Rolf Turner <r.turner at auckland.ac.nz> wrote:

> On 15/06/16 20:18, Jim Lemon wrote:
> > Hi Alice,
> > Have you tried creating a vector of the start position (xpos[1],ypos[1]):
> >
> > xstart<-rep(xpos[1],n)
> > ystart<-rep(ypos[1],n)
> > # where "n" is the number of subsequent positions in the trip
> > max(trackDistance(xstart,ystart,xpos[2:n],ypos[2:n],...))
> >
> > may then give you the value of the longest distance from the start. I
> > don't have the trip package or I could see if you really need to
> > replicate the start positions.
>
> Jim:  This seems to me to be somewhat off the point.  The OP was faced
> with the problem of not being able to access the function homedist().
> This function seems *not* to be exported from the trip package, and yet
> it is a *documented* function which I would assume to imply that users
> should be able to invoke it directly.
>
> It is possible that in the past the OP was dealing with a version of the
> trip package that was created before namespaces came into the picture,
> whence "exporting" was not relevant.  I would suggest that the OP
> contact the package maintainer (maintainer("trip") will give you the
> email address) and enquire as to what is going on.
>
>
This is correct, the maintainer of trip never finished the task and so it's
documented but not exported - but also the CRAN version is incorrect so
please don't use it. Apologies for this.


> In the interim, a workaround *might* be to invoke homedist() as
>
>      trip:::homedist(<whatever>)
>

Please don't do this, the current definition is incorrect. I've updated it
here but can't spend much time checking, any direct input to me is welcome
- perhaps via the Issues feature on the GitHub repository.

https://github.com/mdsumner/trip

Again, my apologies for this.

Cheers, Mike.


> Note the *triple* colon in the foregoing.  I am not at all familiar with
> the trip package so my advice should probably be taken with several
> grains of salt.
>
> cheers,
>
> Rolf Turner
>
> --
> Technical Editor ANZJS
> Department of Statistics
> University of Auckland
> Phone: +64-9-373-7599 ext. 88276
>
> > On Wed, Jun 15, 2016 at 1:43 PM, Alice Domalik <adomalik at sfu.ca> wrote:
> >> Hi List,
> >>
> >> I'm relatively new to R, so apologies if my question is rather
> elementary.
> >> I'm working with some bird tracking data and I would like to calculate
> the maximum distance traveled from the colony.
> >> For the maximum distance traveled, I was going to use the function
> homedist(). However, when I try to use this function I get the following
> error:
> >> Error: could not find function "homedist"
> >> Anyone know why I would get this error? I have been using other
> functions in "trip" without an issue. Is there an alternative way I can
> calculate this?
> >>
> >> Thanks in advance for any help!
>
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-- 
Dr. Michael Sumner
Software and Database Engineer
Australian Antarctic Division
203 Channel Highway
Kingston Tasmania 7050 Australia

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