Some commands that might be useful for your assignments:   >> load file.mat   % Loads the file 'file.mat', containing variables previously saved by the "save" command.   >> i = 37; >> x = X(i)   % If X is a vector, assigns x to the 37th element.   >> i = 37; >> j = 56; >> x= X(i,j)   % If X is a matrix, assigns x to the value of the 56th column of the 37th row.   >> k = 102 >> x = X(k)   % If X is matrix, sets x to element 'k' of the matrix. The elements are first ordered by columns, then by rows.   >> j = 56; >> x = X(:,j)   % Creates a column vector out of the 56th column.   >> i = 37; >> x = X(i,:)   % Creates a row out of the 37th row.   >> x = X(:)   % Creates a vector by concatenating all the values in the matrix X (it goes through columns, then rows)   >> length(x)   % Returns the number of elements in a vector x.   >> [n,d] = size(X)   % Returns the number of rows in a matrix in 'n' and the number of columns in 'd'.   >> x = ones(n,d)   % Creates a matrix of size n by d, where every element is set to 1.   >> x = zeros(n,d)   % Creates a matrix of size n by d, where every element is set to 0.   >> x = 1:n   % Creates a row vector containing the values 1,2,3,...,n.   >> X1 = X(1:n,:)   % Creates a new matrix from the first 1 through n rows of X (useful for cross-validation).   >> X2 = X(n:end,:)   % Creates a new matrix from rows n through to the last row of X (useful for cross-validation).   >> sum(X)   % Computes the sum of all elements of X.   >> max(X)   % If X is a vector, returns the largest element. If X is a matrix, returns the maximum of each column. % Use "min" for finding smallest elements.   >> [maxVal,maxInd] = max(X)   % This returns two arguments. The first, 'maxVal', is the output of the maximum function. % The second, 'maxInd', is the index of the maximal element.   >> unique(X)   % Returns all unique (non-identical) elements of X. >> mode(X); >> mean(X); >> median(X); >> std(X); % If X is a vector, computes the mode/mean/median/standard-deviation of the vector. % If X is a matrix, does this for each column. >> quantile(X,p) % Returns quantile 'p' of X, where 0 <= p <= 1. >> ind = find(X==1) % Returns the indexes of all elements of the vector X, where X(i) = 1.   >> i =1 >> j = 2 >> ind = find(X(:,j)==1) >> mean(X(ind,i))   % Computes the mean of all values in column 'i', that have column 'j' equal to one.   >> plot(x,y)   % Makes a basic line plot with the values of x as the x-axis and the values of y on the y-axis.   >> hist(x)   % Makes a histogram of the values in the vector x.   >> scatter(x,y,size,categories)   % Makes a scatterplot, with the values of x giving the x-locations, the values of y giving the y-locations, size giving the size of the points, and categoires giving the labels used to assign colors.   >> boxplot(y,x)   % Makes a boxplot, where x gives the categories and y gives the values.   >> help sum   % Displays information about how the 'sum' function works.  % Replaces 'sum' with any function for information on how it works.   >> lookfor string   % Displays a list of functions that have 'string' in their description.