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> From: [EMAIL PROTECTED]
> To: r-help@r-project.org
> Date: Sat, 9 Aug 2008 18:25:47 -0400
> Subject: [R] Converting nested "for" loops to an "apply" function(s)
>
>
> Hello,
>
> I would like to know more about how to use the "apply" family and have
> attempted to convert nested "for" loops in example code from Contributed
> Documentation ("The Friendly Beginners' R Course” by Toby Marthews (ZIP,
> 2007-03-01)") to an "apply" function(s). The relevant code is:
>
> distances=c(51,65,175,196,197,125,10,56) #distances of 8 houses from the
> town centre in m
> bearings=c(10,8,210,25,74,128,235,335) #bearings of the houses in
> degrees
>
> xpos=distances*sin(bearings*pi/180) #in sin and cos the argument
> MUST be in radians
> ypos=distances*cos(bearings*pi/180)
>
> numpoints=length(distances)
> nnd=rep(sqrt(2*400*400),times=numpoints) #start with the maximum
> possible distance
> for (i in 1:numpoints) {
> for (j in 1:numpoints) {
> if (i!=j) {
> diffx=abs(xpos[i]-xpos[j])
> diffy=abs(ypos[i]-ypos[j])
> nd=sqrt((diffx^2)+(diffy^2))
> if (nd < nnd[i]) {nnd[i]=nd}
}
}
}
print(data.frame(xpos,ypos,nnd))
My attempts to convert the nested "for" loops to an "apply" function(s) have
not been successful. I would like to know how to convert the code to increase
my knowledge of R programming and to evaluate operational efficiency of the
different strategies.
Thank you in advance for your comments / suggestions.
Kurt Newman
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