[R] change the name of file

[Robert Mcfadden]

Dear R Users,
Is it possible to make file names dependent on a changing variable?
For instance. I generate random numbers in a loop and at each iteration I
want data to write to file (I do not want to write everything in one file
using 'append'):

for (i in 1:50){
x<-matrix(runif(100, min=0,max=1),nrow=5,ncol=20)
Write(t(x),file="Data_i.txt",ncolumns=5,sep="\t") 
}   

Of course file name Data_i.txt will be the same for changing i,
unfortunately. 

Any suggestion would be appreciate
Robert