# Function that finds elements from matrix, and saves the indices of the elements to another matrix Classic List Threaded 3 messages Open this post in threaded view
|

## Function that finds elements from matrix, and saves the indices of the elements to another matrix

 Hi all dear R-list users, This might sound a silly problem, but but for one reason or another it has proved unsolvable to me. I need to solve the following task. I have tried to use two nested for loops as a solution, but have not been able to made it work. It would be great, if someone could formulate a code for me: I need to create a function X that takes as its input a 10x10 matrix, which elements consists of ones and zeros. The function X must find the elements in the matrix A that are "ones", and save the indices of those elements in 2-column matrix, in a following way: the first column has a row number, and the second a column number. The answer should be formulated in a way, that it uses two nested for loops. The matrix to be returned has a maximum of 100 rows, so one possibility exists for a 100x2 matrix filled with zeros in the index and finally separate those rows with zeros. I have tried the following code: A<-matrix(1:0, nrow = 10, ncol = 10) X <- data.frame() for (i in seq(1, nrow(A))) { for (j in seq(1,ncol(A))) { if (A [i,j] > 0) { new_row <- data.frame(Row_number= rownames(A)[i], Column_number= colnames(A)[j]) X <- rbind(X, new_row)   }   } } I only manage to get "Error: object 'X' not found", as a result. thanks in advance for your help. Br. Tuomas         [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.