rownames and colnames with specific value

Question

I have this matrix and i want to get a 2 column matrix, where one column has the rowname and the other column, the colname of cells with value 1

x

   X1 X2 X3
         


        

Answer 1

here another option :

mm <- expand.grid(rownames(mat),colnames(mat))[as.vector(mat==1),]

 Var1 Var2
1    X1   X1
4    X4   X1
6    X2   X2
7    X3   X2
9    X1   X3
11   X3   X3

And to get the OP display , we order by the first column:

 mm[order(mm$Var1),]
   Var1 Var2
1    X1   X1
9    X1   X3
6    X2   X2
7    X3   X2
11   X3   X3
4    X4   X1

Here I mat is your imput , that I reproduce :

mat <- data.frame(X1=c(1,0,0,1),X2=c(0,1,1,0),X3=c(1,0,1,0))
rownames(mat)= paste0('X',1:4)

   X1 X2 X3
X1  1  0  1
X2  0  1  0
X3  0  1  1
X4  1  0  0