change list into interaction matrix

with(dados, ifelse(table(parasito, hospedeiro) > 0, 1, 0))

Hello dear list.
I have a problem that could use some help.
I have a list of parasites and its hosts and want to change it to a
interaction matrix.
I try some functions on the package bipartite put couldn't solve my problem.
If someone could lend a hand i made an example:

#data type example
dados<-data.frame(parasito=c("a","b","b","c","d","d"),
? ? ? ? ? ? ? ? ?hospedeiro=c("1","1","1","2","2","3"))
#how i see them
dados

#i need a matrix like this
matriz<-matrix(data=NA,nrow=length(unique(dados$parasito)),
? ? ? ? ? ? ? ncol=length(unique(dados$hospedeiro)),
? ? ? ? ? ? ? dimnames=list(c(as.character(unique(dados$parasito))),
? ? ? ? ? ? ? c(as.character(unique(dados$hospedeiro)))))

#now i need to fill the matrix with 1 and 0 in presence and absent of
interactions
matriz

#I imagined something like this
#line 1 of the list versus matrix colum 1 and line 1
matriz[1,1]<-ifelse(colnames(matriz)[1]==dados$hospedeiro[1]
? ? ? & rownames(matriz)[1]==dados$parasito[1]
? ? ? ,1,0)

matriz

#line 1 of the list versus matrix colum 2 and line 1
matriz[1,2]<-ifelse(colnames(matriz)[2]==dados$hospedeiro[1]
? ? ? & rownames(matriz)[1]==dados$parasito[1]
? ? ? ,1,0)

matriz

#----------------------------------------

My problem is that with something like this i need to test each matrix
object with all the list. very inefficient.
Can someone see a more efficient an easy solution to do this?

OBS: The example is in portugues, parasito = parasite and hospedeiro = host
:)

--
Grato
Augusto C. A. Ribas