My dataframe consists of projects with the different individuals that took part in it, as well as the year in which projects were carried out.
How can I create, for each year, a nxn relational matrix (n being the number of individuals) that counts the number of collaborations between individuals.
Consider the following example that reproduces the desired structure:
# Example dataframe
set.seed(1)
tp=cbind(paste(rep("project",10),1:10,sep=""),sample(2005:2010,10,replace=T))
tp=tp[sample(1:10,50,T),]
id=sample(paste(rep("id",10),1:10,sep=""),50,T)
df=as.data.frame(cbind(tp,id));rm(tp,id)
names(df)=c("project","year","id")
df=df[order(df$project,df$id),]
df[1:10,]
# project year id
# project1 2006 id1
# project1 2006 id3
# project1 2006 id5
# project1 2006 id5
# project4 2006 id3
# project4 2006 id4
# project5 2006 id3
# project5 2006 id4
# project6 2008 id2
# project6 2008 id3
As an example, a relational matrix for the year 2006 would look like this
id1 id2 id3 id4 id5
id1 0 0 1 0 1
id2 0 0 0 0 0
id3 1 0 0 2 1
id4 0 0 2 0 0
id5 1 0 1 0 0
# link between 1 and 3, 1 and 5, 3 and 5 on project 1
# links between 3 and 4 on project 4 and project 5
# the matrix is symmetric
# the diagonal is O because an individual cannot collaborate with himself
I altered your sampling code a little bit to make the projects dimension differ from the id dimension as I was playing around with the dimensions of the matrices to ensure I was getting the correct n x n matrices. Here's code that works:
set.seed(1)
tp=cbind(paste(rep("project",5),1:5,sep=""),sample(2008:2010,5,replace=T))
tp=tp[sample(1:5,20,T),]
id=sample(paste(rep("id",10),1:10,sep=""),20,T)
df=as.data.frame(cbind(tp,id));rm(tp,id)
names(df)=c("project","year","id")
df=df[order(df$project,df$id),]
spl=split(df,df$year)
net=lapply(spl,function(x){
m = table(x$id, x$project)
res = tcrossprod(m) ## equivalently: res = m %*% t(m)
diag(res) <- 0
res <- ifelse(res > 0, 1, 0)
res
})
net
Split Data:
$`2008`
project year id
5 project1 2008 id4
7 project1 2008 id6
19 project1 2008 id6
2 project5 2008 id1
13 project5 2008 id2
1 project5 2008 id4
16 project5 2008 id9
$`2009`
project year id
9 project2 2009 id2
6 project2 2009 id5
20 project2 2009 id6
17 project2 2009 id7
14 project2 2009 id8
11 project3 2009 id7
$`2010`
project year id
3 project4 2010 id4
8 project4 2010 id5
15 project4 2010 id5
12 project4 2010 id8
18 project4 2010 id8
4 project4 2010 id9
10 project4 2010 id9
Adjacency matrices by project for each year:
$`2008`
id1 id2 id4 id5 id6 id7 id8 id9
id1 0 1 1 0 0 0 0 1
id2 1 0 1 0 0 0 0 1
id4 1 1 0 0 1 0 0 1
id5 0 0 0 0 0 0 0 0
id6 0 0 1 0 0 0 0 0
id7 0 0 0 0 0 0 0 0
id8 0 0 0 0 0 0 0 0
id9 1 1 1 0 0 0 0 0
$`2009`
id1 id2 id4 id5 id6 id7 id8 id9
id1 0 0 0 0 0 0 0 0
id2 0 0 0 1 1 1 1 0
id4 0 0 0 0 0 0 0 0
id5 0 1 0 0 1 1 1 0
id6 0 1 0 1 0 1 1 0
id7 0 1 0 1 1 0 1 0
id8 0 1 0 1 1 1 0 0
id9 0 0 0 0 0 0 0 0
$`2010`
id1 id2 id4 id5 id6 id7 id8 id9
id1 0 0 0 0 0 0 0 0
id2 0 0 0 0 0 0 0 0
id4 0 0 0 1 0 0 1 1
id5 0 0 1 0 0 0 1 1
id6 0 0 0 0 0 0 0 0
id7 0 0 0 0 0 0 0 0
id8 0 0 1 1 0 0 0 1
id9 0 0 1 1 0 0 1 0