[R] Subtracting elements of a vector from each other stepwise

[Ben Harrison]

If I were Michael (OP) right now, I think my head would be spinning.

As a newbie myself, I know how hard it is to read R code for the first 
time, so could it also be part of the newsgroup etiquette to at least 
partially explain provided code to newbies?

I agree that the interactive help '?' is available and should be 
consulted, but it would also be helpful if those of you with great 
experience could add a little guidance for your code.

Excuse me if this is out-of-place.

Ben


On 11/09/13 09:48, Ben Bolker wrote:
> On 13-09-10 06:24 PM, arun wrote:
>> Hi,
>> May be this also works:
>>
>>   dist(x)
>> #   1  2  3
>> #2  2
>> #3  6  4
>> #4 12 10  6
>>
>> as.matrix(dist(x))
>> #   1  2 3  4
>> #1  0  2 6 12
>> #2  2  0 4 10
>> #3  6  4 0  6
>> #4 12 10 6  0
>> which(dist(x)==min(dist(x)))
>> #[1] 1
>> A.K.
>
>    Yes, but you need to set the diagonal to NA, or something -- the OP
> doesn't want to include self-comparison. It also helps to use
> arr.ind=TRUE in which().  You're right that dist() would be a hair more
> efficient that outer(...), though
>
>>
>>
>>
>> ----- Original Message -----
>> From: Ben Bolker <bbolker at gmail.com>
>> To: r-help at stat.math.ethz.ch
>> Cc:
>> Sent: Tuesday, September 10, 2013 5:39 PM
>> Subject: Re: [R] Subtracting elements of a vector from each other stepwise
>>
>> arun <smartpink111 <at> yahoo.com> writes:
>>
>>>
>>> Hi,
>>> Not sure this is what you wanted:
>>>
>>>   sapply(seq_along(x), function(i) {x1<- x[i]; x2<- x[-i];
>> x3<-x2[which.min(abs(x1-x2))];c(x1,x3)})
>>> #     [,1] [,2] [,3] [,4]
>>> #[1,]   17   19   23   29
>>> #[2,]   19   17   19   23
>>> A.K.
>>
>>
>>    It's a little inefficient (because it constructs
>> the distances in both directions), but how about:
>>
>> x = c(17,19,23,29)
>> d <- abs(outer(x,x,"-"))
>> diag(d) <- NA
>> d[lower.tri(d)] <- NA
>> which(d==min(d,na.rm=TRUE),arr.ind=TRUE)
>>
>>
>> ?
>>
>>> ----- Original Message -----
>>> From: Michael Budnick <mbudnick08 <at> snet.net>
>>> To: r-help <at> r-project.org
>>> Cc:
>>> Sent: Tuesday, September 10, 2013 4:06 PM
>>> Subject: [R] Subtracting elements of a vector from each other stepwise
>>>
>>> I am trying to figure out how to create a loop that will take the
>>> difference of each member of a vector from each other and also spit out
>>> which one has the least difference.
>>>
>>> I do not want the vector member to subtract from itself or it must be able
>>> to disregard the 0 obtained from subtracting from itself.
>>>
>>> For example:
>>>
>>> x = c(17,19,23,29)
>>
>>
>> [snip]
>>
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>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>