R Exercises | Programming Exercises for Finance in the R Language

Math and Stats: Exercises

6. Matrix addition. You are given two matrices: X, Y, and Z. You can check the dimensions of each object in R with the dim() function.

In order to perform matrix addition, the dimensions of the two matrices must be identical. Figure out which matrix can be added to X and add it. You can add two matrices using the + operator.



                                X <- matrix(c(0,0,0,0,0,0,0,0,0,0,0,0), nrow=3, ncol=4)
                                Y <- matrix(c(1,2,3,4,5,6,7,8,9,10,11,12), nrow=4, ncol=3)
                                Z <- matrix(c(1,2,3,4,5,6,7,8,9,10,11,12), nrow=3, ncol=4)



                            # Compute the dimensions of X.
                            ___(X)

                            # Compute the dimensions of Y.
                            ___

                            # Compute the dimensions of Z.
                            ___

                            # Add the correct matrix to X.
                            X ___ ___



                            # Compute the dimensions of X.
                            dim(X)

                            # Compute the dimensions of Y.
                            dim(Y)

                            # Compute the dimensions of Z.
                            dim(Z)

                            # Add the correct matrix to X.
                            X + Z


                            test_error()
                            test_function("dim", incorrect_msg="Did you use the `dim()` function?")
                            success_msg("Excellent work. Notice that X+Z = Z. What type of matrix is X?")

You can use the dim() function to check a matrix's dimensions.

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