tm package: Output of findAssocs() in a matrix instead of a list in R

Question

Consider the following list:

library(tm)
data("crude")
tdm <- TermDocumentMatrix(crude)
a <- findAssocs(tdm, c("oil", "opec", "xyz"), c(0.7, 0.75, 0.1))

How do I manage to have a data frame with all terms associated with these 3 words in the columns and showing:

1. The corresponding correlation coefficient (if it exists)
2. NA if it does not exists for this word (for example the couple (oil, they) would show NA)

Answer 1

Here's a solution using reshape2 to help reshape the data

library(reshape2)
aa<-do.call(rbind, Map(function(d, n) 
    cbind.data.frame(
      xterm=if (length(d)>0) names(d) else NA, 
      cor=if(length(d)>0) d else NA, 
      term=n),
    a, names(a))
)

dcast(aa, term~xterm, value.var="cor")