[英]R get highest x cells and their rownames/colnames in a symmetric matrix?
I have a symmetric matrix mat
: 我有一个对称矩阵
mat
:
A B C
A 1 . .
B . 1 .
C . . 1
And I want to calculate the two highest elements of it. 我想计算其中的两个最高元素。 Now since it's a symmetric matrix I thought of using
upper.tri
like so: 现在,由于它是一个对称矩阵,因此我想到像这样使用
upper.tri
:
mat.tri<-upper.tri(mat) # convert to upper tri
mat.ord<-order(mat.tri,na.last=TRUE,decreasing=TRUE)[1:2] # order by largest
a.ind<-which(mat%in%mat.tri[mat.ord]) # get absolute indices
r.ind<-arrayInd(a.ind,dim(mat)) # get relative indices
# get row/colnames using these indices
So the above is such a roundabout way of doing things, and even then the output has 'duplicate' rows in that they are just transposed.. 因此,以上是这种回旋处理方式,即使这样,输出仍具有“重复”行,因为它们只是转置了。
Anyone got a more intuitive way of doing this? 有人有更直观的方法吗?
Thanks. 谢谢。
Liberally borrowing from the excellent ideas of @SimonO'Hanlon
and @lukeA
, you can construct a two-liner function to do what you want. 自由地借鉴
@SimonO'Hanlon
和@lukeA
的出色思想,您可以构造一个两层函数来完成您想要的事情。 I use: 我用:
arrayInd()
to return the array index arrayInd()
返回数组索引 order()
to order the upper triangular elements order()
对上三角元素进行排序 NA
, using m[lower.tr(m)] <- NA
m[lower.tr(m)] <- NA
将下三角矩阵设置为NA
的其他技巧 Try this: 尝试这个:
whichArrayMax <- function(m, n=2){
m[lower.tri(m)] <- NA
arrayInd(order(m, decreasing=TRUE)[seq(n)], .dim=dim(m))
}
mat <- matrix( c(1,2,3,2,1,5,3,5,1) , 3 , byrow = TRUE )
mat
[,1] [,2] [,3]
[1,] 1 2 3
[2,] 2 1 5
[3,] 3 5 1
whichArrayMax(mat, 2)
[,1] [,2]
[1,] 2 3
[2,] 1 3
arrayInd(which.max(mat), .dim=dim(mat))
它与@ SimonO'Hanlon中的which( mat == max(mat) , arr.ind = TRUE )[1,]
相同,但效率更高。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.