Add support for VNA graph files

[gvegayon]

SOURCE: https://gephi.org/users/supported-graph-formats/netdraw-vna-format/

The VNA format is commonly used by Netdraw, and is very similar to Pajek format. It defines nodes and edges (ties), and supports attributes. Each section of the file is separated by an asterisk.

More details about the format can be found in Netdraw’s manual.

Basic example
The VNA sample below shows a graph with 3 nodes and 4 edges. Each section has a column header line. The “ties” are edges, and ‘from’ and ‘to’ defines the direction. The ’strength’ attribute encodes the weight of the edge.

*node data
ID name gender age
j101 joe male 56
w067 wendy female 23
b303 bill male 48
*tie data
from to strength
j101 w067 1
w067 j101 2
j101 b303 1
w067 b303 5

With node properties
This example from the VNA manual includes properties for nodes, like position or labels. Gephi supports X, Y, SIZE, COLOR (int between 0 and 255, only red) and SHORTLABEL.

*Node data
ID, gender, role, betweenness
HOLLY female participant 78.33333588
BRAZEY female participant 0
CAROL female participant 1.333333373
PAM female participant 32.5
PAT female participant 39.5
JENNIE female participant 6.333333492
PAULINE female participant 12.5
ANN female participant 0.5
MICHAEL male participant 58.83333206
BILL male participant 0
LEE male participant 5
DON male participant 16.33333397
JOHN male participant 0
HARRY male participant 2.333333254
GERY male instructor 54.66666794
STEVE male instructor 16.83333397
BERT male instructor 13.66666698
RUSS male instructor 47.33333206
*Node properties
ID x y color shape size shortlabel
HOLLY 1160 271 255 1 10 HOLLY
BRAZEY 1214 577 255 1 10 BRAZEY
CAROL 671 612 255 1 10 CAROL
PAM 985 127 255 1 10 PAM
PAT 802 402 255 1 10 PAT
JENNIE 729 187 255 1 10 JENNIE
PAULINE 69 590 255 1 10 PAULINE
ANN 877 818 255 1 10 ANN
MICHAEL 182 224 255 1 10 MICHAEL
BILL 380 137 255 1 10 BILL
LEE 617 44 255 1 10 LEE
DON 281 656 255 1 10 DON
JOHN 617 839 255 1 10 JOHN
HARRY 382 410 255 1 10 HARRY
GERY 1051 706 255 1 10 GERY
STEVE 64 394 255 1 10 STEVE
BERT 348 812 255 1 10 BERT
RUSS 1176 426 255 1 10 RUSS
*Tie data
from to friends strength
HOLLY PAM 1 1
PAT HOLLY 1 2
PAULINE PAT 1 2
JOHN RUSS 1 3
HARRY HOLLY 1 2
HARRY MICHAEL 1 1
BERT RUSS 1 3
RUSS GERY 1 1
RUSS STEVE 1 3
RUSS BERT 1 2
HOLLY BRAZEY 0 7
HOLLY CAROL 0 17
BRAZEY PAULINE 0 7
BRAZEY ANN 0 6
BRAZEY MICHAEL 0 15
PAM MICHAEL 0 9
PAM BILL 0 16
PAM LEE 0 13
JENNIE BRAZEY 0 8
PAULINE JENNIE 0 5
PAULINE ANN 0 4
ANN PAT 0 7
ANN MICHAEL 0 9
BILL LEE 0 10
DON ANN 0 12