MATLAB clear Command

clear Command

• The clear command removes all variables from the workspace.
• It does not save variables to a file, nor is it used to create new variables.
• The clear command does not remove only temporary variables from the workspace.
• It can be used to remove individual variables.

Working with Matrices

• Matrices in MATLAB can be created using square brackets [], for example, x = [1 2 3; 4 5 6];

Summation

• sum(x) returns the sum of the elements of x as a row vector with the sum over each column
• sum(x,2) sums along the dimension 2 (i.e., sums each row)
• To find the sum of elements stored in a matrix with n dimensions, use sum command n times in cascade form

Mean

• mean(x) returns the average of the elements of x as a row vector with the average over each column
• mean(x,2) averages along the dimension 2 (i.e., averages each row)
• mean(mean(x)) can be used to find the overall mean of a matrix

Creation of Matrices

• zeros(N) produces an N by N matrix of zeros
• zeros(N,M) produces an N by M matrix of zeros
• ones(N) produces an N by N matrix of ones
• ones(N,M) produces an N by M matrix of ones

Matrix Indexing

• A(1,4) refers to the element in the first row and fourth column of matrix A
• A(1,4) + A(2,4) + A(3,4) + A(4,4) can be used to compute the sum of the elements in the fourth column of A
• sum(A(:,4)) can also be used to compute the sum of the elements in the fourth column of A

Colon Operator

• The colon : is a powerful operator in MATLAB
• 1:10 returns a row vector containing the integers from 1 to 10
• 100:-7:50 returns a row vector containing the integers from 100 to 50 in decrements of 7
• A(1:k,j) returns the first k elements of the jth column of A
• A(4,:) returns the entire fourth row of A

Basic Matrix Functions

• min(x) returns the minimum value of the elements of x
• min(min(x)) returns the minimum value of the minimum values of each column of x
• magic(N) produces an N by N magic square
• inv(x) returns the inverse of matrix x
• diag(x) returns the diagonal of matrix x
• prod(x) returns the product of the elements of x as a row vector with the product over each column
• median(x) returns the median value of the elements of x

This quiz covers the functionality of the clear command in MATLAB, including its effects on variables in the workspace.