[R] evaluating string variables

[Romain Francois]

Le 12.08.2005 16:44, Leonardo Sepulveda Durán a écrit :

>Hello!!!
>
>I have a folder (C:/R/) with matrix files, named by number, i.e.
>0.mat, 1.mat,...,1250.mat. In this case, they are 5x5 simetric
>matrices. I would like to compute a property for each matrix and put
>calculated values into a data frame for posterior ploting and
>printing. Below there is an example for 7 matrices (0.mat..6.mat)
>
>#define data frame
>L <- data.frame(frame=numeric(7), L=numeric(7))
>f0<-1/(5*(5-1)) # first variable for computation
>
>#loop over matrices, Open it , calculate property and put into data frame
>for(i in 0:6){
>	m<-matrix(scan('C:/R/i.mat', n=5*5),5,5, byrow=TRUE) # load matrix
>	f1<-geodist(m)                                                           
>	f2<-sum(colSums(f1$gdist))                                        
>	l <-f0*f2                                                            
>       # Calculate property
>	L[i+1, ]<-c(i,l)                                                     
>      # Fill data frame
>}
>
>but the matrix cannot be loaded, because it try to open a file named
>"i.mat". I don`t know how to loop with a counter named 'i', and use it
>to define the name of the file too. How can i do it? I have not found
>the way.
> 
>Leonardo
>  
>
Here are two ways :

paste('C:/R/',i,'.mat',sep="")
sprintf("C:/R/%d.mat",i)

Romain

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