Data format for MultiNet
MultiNet uses two files of data -- one describes node attributes and the other describes the links between nodes.
The data formats for both attribute and network data are intended to:
a) allow for multiple attributes and networks (hence the name MultiNet)
b) use a minimum amount of space (both on disk and in memory)
c) be easy to edit and maintain (the files are self-documenting)
The data format is an outgrowth of formats used by both NEGOPY and FATCAT (Richards, 1995, 1999a, 1999b).
MultiNet uses a pair of files with the same names and different extensions. The extensions are always .NOD for NODE (actor attributes) and .LIN for LINK (network attributes). The example we give here is VICKCHAN.NOD and VICKCHAN.LIN, which is the Vickers and Chan data analysed in (WP). The .NOD file describes the sex of the children (only one Node variable here). The .LIN file describes who children say they "Get on with", and who they "Work with" (two network Link variables). Each file begins with a header which defines the variables, and where they occur in the file (by column numbers). Where it makes sense, some of the variables may also have value labels. If no labels are defined, the actual values are used in reports. Tables 2a and 2b show these two files, each with the first few lines of data.
Table 2a. Format of a .NOD
file
| ID (1-3) | Actor identifier |  |
header | ||
| SEX (4-5) | Attribute SEX | ||||
| / | Mark start of value lables | ||||
| 1 boy 2 girl |
value labels | ||||
| / | Mark end of value labels | ||||
| END | End of header | ||||
| 1 1 2 1 : : |
 |
data | |||
| ID (1-3) | Link is FROM this actor | |
header |
||
| Get on with(7-8) | does i "get on with" j? | ||||
| / | Mark start of value labels | ||||
|
0 No |
value labels | ||||
| / | Mark end of value labels | ||||
| Work with(9-10) | does i "work with" j? | ||||
| / | Mark start of value labels | ||||
| 0 No 1 Yes |
value labels | ||||
| / | Mark end of value labels | ||||
| END | End of header | ||||
| 1 2 0 1 1 5 0 1 : : |
|
data | |||
MultiNet does not use adjacency matrices, either as data files or internally. All calculations use sparse methods. If your data is in the form of an adjacency matrix, the program Adj2Neg (Richards, 1998a) will automatically produce the correct data format for the Link file. If your data is in a free format file with comma, space, or tab delimiters, the Free2Fix program (Richards, 1998b) will convert it to MultiNet format quickly and easily. Adj2Neg and Free2Fix are available at http://www.sfu.ca/~richards.
You will still need to add appropriate header information, and an actor attribute file. If your data is in the format used by NEGOPY (Richards, 1995, 1999a) or PAJEK (Batagelj and Mrvar, 2000), you can make the two required files without too much effort. Network data in other formats will require some programming (possibly via a spreadsheet). Examples of correct .NOD and .LIN files are provided with the MultiNet package, also available at the same URL.
Once the correct data files are available, the MultiNet FILE IMPORT menu selection will read the two files. A certain amount of error-detection and on-the-fly editing is supported. When the files are successfully imported, the Node and Link variables are shown in a pair of windows, and are available to all the MultiNet data analysis and recoding options, in particular, to MODELS PSTAR from the main menu bar. The other options are beyond the scope of this article.
The example above shows the plain ASCII fixed-format style that MultiNet uses. With this approach, the location of each variable is given in the header. The SEX attribute variable in the .NOD file occupies the fourth and fifth characters of each line of data. Since it is a one-digit value ("1" or "2"), the number will always be the fifth character on each line.
Recent versions of MultiNet can also read the comma-delimited files that can be produced by most spreadsheet programs.
REFERENCES
Richards, W.D. (1995) NEGOPY 4.30 Manual and user's Guide. 174 pp. School of Communi-cation, SFU.
Richards, W.D. Adj2Neg. (1998a). A computer program for converting adjacency matrices to NEGOPY-style data. http://www.sfu.ca/~richards/Pages/utility.htm#ADJ2NEG
Richards, W.D. Free2Fix. (1998b) A computer program that parses and converts free-format files into fixed-format files for MultiNet. http://www.sfu.ca/~richards/Pages/utility.htm#Free2Fix
Richards, W.D. (1999a) NEGOPY Manual in Acrobat format. http://www.sfu.ca/~richards/Pdf-ZipFiles/negman98.pdf
Richards, W.D. (1999b) FATCAT: A different kind of network analysis program. http://www.sfu.ca/~richards/Pdf-ZipFiles/fatman2.pdf
Seary, A. (1999) PSPAR: Sparse Matrix Version of PSTAR. http://www.sfu.ca/~richards/pspar5k.zip