[R] building a spatial matrix

[A M Lavezzi]

Hello,

I have a sample of 1327  locations, each one idetified by an id and a
numerical code.

I need to build a spatial matrix, say, M, i.e. a 1327x1327 matrix
collecting distances among the locations.

M(i,i) should be 0, M(i,j) should contain the distance among location i and
j

I shoud use data organized in the following way:

1) id_cell contains the identifier (id) of each location (1...1327) and the
numerical code of the location (f_cell) (see head of id_cell below)

> head(id_cell)
     id  f_cell
1    1   2120
12  2     204
22  3   2546
24  4   1327
34  5   1729
43  6   2293

2) censDist contains, for each location identified by its numerical code,
the distance to other locations (censDist has 1.5 million rows). The
head(consist) below, for example, reads like this:

location 2924 has a distance to 2732 of 1309.7525
location 2924 has a distance to 2875 of 696.2891,
etc.

> head(censDist)
  f_cell f  _cell_neigh  distance
1   2924         2732   1309.7525
2   2924         2875     696.2891
3   2924         2351   1346.0561
4   2924         2350   1296.9804
5   2924         2725   1278.1877
6   2924         2721   1346.9126


Basically, for every location in  id_cell I should pick up the distance to
other locations in id_cell from censDist, and allocate it in M

I have not come up with a satisfactory vectorizion of this problem and
using a loop is out of question.

Thanks for your help
Mario


-- 
Andrea Mario Lavezzi
DiGi,Sezione Diritto e Società
Università di Palermo
Piazza Bologni 8
90134 Palermo, Italy
tel. ++39 091 23892208
fax ++39 091 6111268
skype: lavezzimario
email: mario.lavezzi (at) unipa.it
web: http://www.unipa.it/~mario.lavezzi

	[[alternative HTML version deleted]]