[R] Query to find minimum value in a matrix in R

[S Ellison]

> I am unable to understand the line in red code 
Colour does not survive plain text transmission; try adding comments (# ...) instead, or state which line of code you do not understand.

In the mean time you could take a look, first, as 
?cbind
?apply
?'[' 

with particular attention to the meaning of negative indices (like '-n' in dd[-n,])

S Ellison



> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of susmita T
> Sent: 16 September 2016 13:09
> To: r-help at r-project.org
> Subject: [R] Query to find minimum value in a matrix in R
> 
> Hi,
> Good Morning! I am new to R and finding difficulty in understanding the code.
> Since few days I am stuck at single line of code which I am unable to
> understand.
> Though there may be number of logics to find min value. As a new beginner I
> am following a book and as it has the following code
> 
> mind<-function(d)
> {
> 	n<-nrow(d)
> 	dd<-cbind(d,1:n)
> 	wmins<-apply(dd[-n,],1,imin)
> 	i<-which.min(wmins[2,])
> 	j<-wmins[1,i]
> 	return(c(d[i,j],i,j))
> }
> imin<-function(x)
> {
> 	lx<-length(x)
> 	i<-x[lx]
> 	j<-which.min(x[(i+1):(lx-1)])
> 	k<-i+j
> 	return(c(k,x[k]))
> }
> 
> So when executed this with mind(below matrix) I get
> 0	12	13	8	20
> 12	0	15	28	88
> 13	15	0	6	9
> 8	28	6	0	33
> 20	88	9	33	0
> the answer as 6 , row 3 column 4
> 
> Due to the symmetry of the matrix , the skipping of the early part of row is
> done by using expression (x[(i+1):(lx-1)])..(which is in red color in the code
> shown above). I am unable to understand the line in red code and how it is
> implemented in the line 5(i.e wins)…(shown in pink color in the code above I
> have done necessary homework to understand but still finding it hard to get it.
> Please someone help.
> 
> 
> 	[[alternative HTML version deleted]]
> 
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> and provide commented, minimal, self-contained, reproducible code.


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