R Exercises | Programming Exercises for Finance in the R Language

Matrix Algebra: Exercises

2. Matrix addition. The matrix, A, and the vector, b have been defined for you. Use the functions nrow() and ncol() to calculate the number of rows and columns of the matrix. Use this information to convert b into a matrix, C, that can be added to A.


                                  A <- matrix(1:30, nrow = 5, ncol = 6)
                                  b <- c(31:60)



                              # Compute number of rows in A.
                              rowsA <- nrow(___)

                              # Compute number of columns in A.
                              colsA <- ___(___)

                              # Reshape vector, b, into matrix, C, with same dimensions as A.
                              C <- ___(___, nrow = rowsA, ncol = ___)

                              # Print sum of A and C.
                              print(A+C)



                                # Compute number of rows in A.
                                rowsA <- nrow(A)

                                # Compute number of columns in A.
                                colsA <- ncol(A)

                                # Reshape vector, b, into matrix, C, with same dimensions as A.
                                C <- matrix(b, nrow = rowsA, ncol = colsA)

                                # Print sum of A and C.
                                print(A+C)


                              test_error()
                              test_object("rowsA", incorrect_msg="Did you use the function `nrows()`?")
                              test_object("colsA", incorrect_msg="Did you use the function `ncols()`?")
                              test_object("C", incorrect_msg="Did you use `nrowsA` and `ncolsA` as arguments?")
                              success_msg("Good work.")

Recall that the matrix() function can specify a number of rows and a number of columns.

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