====== Dual hypernet ======

<code>
> hyper.dual <- function(HN){
+   HD <- HN
+   HD$info$creator <- c(HN$info$creator,"hyper.dual")
+   HD$info$date <- c(HN$info$date,date())
+   HD$info$nNodes <- HN$info$nLinks; m <- HD$info$nLinks <- HN$info$nNodes
+   HD$nodes <- subset(HN$links,select=-c(E)); HD$links <- HN$nodes
+   E = vector(mode="list",m)
+   for(i in 1:m) E[[i]] <- which(sapply(HN$links$E,function(x) i %in% x)) 
+   HD$links$E <- E
+   return(HD)
+ }
</code>

<code>
> HN$info$title
[1] "Network file formats and tools"
> str(HN)
List of 5
 $ format: chr "hypernets"
 $ info  :List of 9
  ..$ network: chr "NetFormats"
  ..$ title  : chr "Network file formats and tools"
  ..$ by     : chr "Gao etal."
  ..$ href   : chr [1:2] "https://www.cell.com/patterns/pdf/S2666-3899(23)00218-0.pdf" "https://github.com/bavla/symData/tree/master/SDAJSON"
  ..$ creator: chr "V. Batagelj"
  ..$ date   : chr "Sun Nov 12 15:52:36 2023"
  ..$ nNodes : int 7
  ..$ nLinks : int 8
  ..$ simple : logi NA
 $ nodes :'data.frame': 7 obs. of  1 variable:
  ..$ ID: chr [1:7] "EasyGraph" "NetworkX" "igraph" "SNAP" ...
 $ links :'data.frame': 8 obs. of  2 variables:
  ..$ ID: chr [1:8] "Edge List" "GraphML" "GML" "Pickle" ...
  ..$ E :List of 8
  .. ..$ : int [1:5] 1 2 3 4 6
  .. ..$ : int [1:6] 1 2 3 5 6 7
  .. ..$ : int [1:6] 1 2 3 5 6 7
  .. ..$ : int [1:4] 1 2 3 5
  .. ..$ : int [1:4] 1 2 3 6
  .. ..$ : int [1:5] 1 3 4 5 6
  .. ..$ : int [1:2] 1 6
  .. ..$ : int [1:2] 1 6
 $ data  : list()
> HD <- hyper.dual(HN)
> str(HD)
List of 5
 $ format: chr "hypernets"
 $ info  :List of 9
  ..$ network: chr "NetFormats"
  ..$ title  : chr "Network file formats and tools"
  ..$ by     : chr "Gao etal."
  ..$ href   : chr [1:2] "https://www.cell.com/patterns/pdf/S2666-3899(23)00218-0.pdf" "https://github.com/bavla/symData/tree/master/SDAJSON"
  ..$ creator: chr [1:2] "V. Batagelj" "hyper.dual"
  ..$ date   : chr [1:2] "Sun Nov 12 15:52:36 2023" "Mon Nov 13 01:27:24 2023"
  ..$ nNodes : int 8
  ..$ nLinks : int 7
  ..$ simple : logi NA
 $ nodes :'data.frame': 8 obs. of  1 variable:
  ..$ ID: chr [1:8] "Edge List" "GraphML" "GML" "Pickle" ...
 $ links :'data.frame': 7 obs. of  2 variables:
  ..$ ID: chr [1:7] "EasyGraph" "NetworkX" "igraph" "SNAP" ...
  ..$ E :List of 7
  .. ..$ : int [1:8] 1 2 3 4 5 6 7 8
  .. ..$ : int [1:5] 1 2 3 4 5
  .. ..$ : int [1:6] 1 2 3 4 5 6
  .. ..$ : int [1:2] 1 6
  .. ..$ : int [1:4] 2 3 4 6
  .. ..$ : int [1:7] 1 2 3 5 6 7 8
  .. ..$ : int [1:2] 2 3
 $ data  : list()
</code>

<code>

</code>