Some commands that might be useful for your assignments:

>> 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.

>> load file.mat
% Load 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.

>> X2 = X(n:end,:)
% Creates a new matrix from rows n through to the last row of X.

>> 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.

>> x = A\b
% Sets x to a solution (if one exists) of Ax =b.