2+2 Just type and press enter and the answer comes up ans = 4

Transcription

1 Demonstration Red text = commands entered in the command window Black text = Matlab responses Blue text = comments 2+2 Just type and press enter and the answer comes up 4 sin(4)^ The elementary functions are quite logical. Arithmetic operations (+ - * /) are the same as everywhere. Power is denoted by ^ (in Matlab 6.5 there is a bug: The ^ sign has to be pressed twice) 1/5 There is continuity between number classes: It does not matter if the numbers are integer, real or complex.2 i*i -1 i is the complex number pi there are other pre-defined numbers such as pi format long makes more numbers become printed pi help format To get help about a command, type help + command FORMAT Set output format. All computations in MATLAB are done in double precision. FORMAT may be used to switch between different output display formats as follows: FORMAT Default. Same as SHORT. FORMAT SHORT Scaled fixed point format with 5 digits. FORMAT LONG Scaled fixed point format with 15 digits. FORMAT SHORT E Floating point format with 5 digits. FORMAT LONG E Floating point format with 15 digits. FORMAT SHORT G Best of fixed or floating point format with 5 digits. FORMAT LONG G Best of fixed or floating point format with 15 digits. FORMAT HEX Hexadecimal format. FORMAT + The symbols +, - and blank are printed for positive, negative and zero elements. Imaginary parts are ignored. FORMAT BANK Fixed format for dollars and cents. FORMAT RAT Approximation by ratio of small integers. Spacing: FORMAT COMPACT Suppress extra line-feeds. FORMAT LOOSE Puts the extra line-feeds back in.

2 help exp EXP Exponential. EXP(X) is the exponential of the elements of X, e to the X. For complex Z=X+i*Y, EXP(Z) = EXP(X)*(COS(Y)+i*SIN(Y)). Page 1 Demo The help contains info about related functions, demos etc See also LOG, LOG1, EXPM, EXPINT. Overloaded methods help sym/exp.m a = 2 a = 2 Assigns a value to a variable b = 3; A semicolon after the command supresses printing the respons [2,3,4;5,6,7] To write a matrix: Enter columns separated by commas, rows separated by semi-colons. The expression should be surrounded by brackets B = [2 3 6; pi i] B = Column 1 2. Column 2 3. Column i The commas can be replaced by blanks A(1,2) 3 To get hold of an element in the matrix use the indices: A(row,column) A(1,2)= 2 4 The indices can also be used to set a value of a single element C =[A;A] C = Several matrices can be appended to each other by use of the semi-colon (adds new lines)

3 D = [B,B] Several matrices can be appended to eachother by use of the comma (adds new columns) D = Column 1 2. Page 2 Demo Column 2 3. Column i Column 4 2. Column 5 3. Column i format short To return to short format D(3,2) = 2 If an element is specified that is outside the range of the matrix (here the 2nd value of the 3rd line is set to zero, but there are only 2 lines in the matrix) - then the matrix is expanded (the new slots are filled with zeros) D = Columns 1 through 3 2 The assigned value is blue here Columns 4 through 6 D(3,2,2) = 1 The dimension of the matrix can also be increased (here to 3 dimensions: There is no limit) D(:,:,1) = Columns 1 through 3 Columns 4 through 6 D(:,:,2) = 1

4 1:5 The colon operator is special. Placed between two numbers it is used for incrementation (øh?), i.e. it means the sequence between the numbers :.1:.16 If placed between three numbers it means incrementation by the specified step-size A(1,1:3)=4: Secuences can also be used to assign values. t = linspace(,5,1); There are several other ways to create matrices. Linspace here creates a vector with 1 elements, linearly spaced between and 1 f = sin(t); g = exp(-t).*cos(t); Most functions work elementwise on the matrix Except for multiplication, division and power which are matrix multiplication, division etc. For element-wise multiplication, division & power put a dot in front of the command (.* and./ and.^) plot(t,f) plot(t,f,t,g) plots f as a function of t plots f as a function of t and g as a function of t in the same graph R = rand(5,1); There are several special matrices - here 5x1 matrix with random numbers between and 1 E = eye(5) The unity matrix (here 5x5) E = F = A' F = Matrix arithmetic: 'fly-dot' means transpose S = sparse(e) S = (1,1) 1 (2,2) 1 (3,3) 1 (4,4) 1 (5,5) 1 Sparse matrices: Use sparse to increase computational speed

5 helpdesk Opens the helpdesk (guided help: They have a much better video demonstration) (Click Begin Here - Matrices and Arrays - Entering Matrices)