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If some functions of your submitted work are in sub-directories, the Matlab path must be set at the beginning of your code, e.g. like this
if( ~exist( 'figexport', 'file' ) ) addpath tools end if( ~exist( 'my_specific_function', 'file' ) ) addpath my_library end
plot
help plot % text version doc plot % html version
Matlab has a powerful debugger. Either put breakpoints everywhere you want, or use the command keyboard in your code to stop processing at the place. Exit the debugging mode:
keyboard
dbquit
You can also start debugging automatically in case of error by turning on
dbstop error
Especially when some user input is needed, it is wise to store intermediate data for later reuse. Following example could be helpful
if( ~exist( 'my_points.mat', 'file' ) ) [x y] = ginput( 7 ); save( 'my_points.mat', 'x', 'y' ); else load( 'my_points.mat' ); end
Vectors are stored as column matrices.
u = [1;2]; X = [1;2;3]; Xmore = [1 2 3; 4 5 6]'; % transpose at the end
Vectors are multiplied by a matrices on the left:
P = [1 0 0 -5; 0 1 0 -6; 0 0 1 1]; % a camera ux_homog = P * [X;1]; % projection
I = eye(3); % 3x3 identity I2 = diag( [1 1 1] ); % same result Z = zeros(3); % 3x3 matrix of zeroes O = ones(3); % 3x3 matrix of ones
X1 = [1;2;3]; X2 = [4;5;6]; d2 = norm(X1-X2); % cannot be used for more vectors d2 = sqrt(sum((X1-X2).^2)); % for matrices with points stored in columns
u1 = [4;5;1]; u2 = [7;8;1]; dot12 = u1' * u2; % apostrophe is the transpose
In addition to standard matrix addition and subtraction, there are some operators working element-by-element.
M1 = [1 2; 3 4; 5 6]; M2 = [7 8; 9 10; 11 12]; % note the sizes A = M1 .* M2; % Hadamard product (multiplication element-by-element; note the dot) B = M1 ./ M2; % Hadamard division (division element-by-element) C = M1 .^ 2; % power element-by-element
numbers = [1 2 sqrt(-3) acos(2) 4 6+3i 7 ]; is_real = imag( numbers ) == 0; % logical array real_only = numbers( is_real );
u1 = [4;5;1]; u2 = [7;8;1]; u12x = cross(u1,u2); % verification of orthogonality by dot product % (remember the recommendations 1 and 2) u12x' * u1 % should be zero u12x' * u2 % should be zero
Let x = r cos(a) and y = r sin(a). Then the angle can be recovered as
a = atan2( y, x );
This function is safe when either of its arguments is zero (but not both), and works for four quadrants.
Let hnd be some axes handle (e.g. gca) or some figure handle (e.g. gcf). The snapshot identical to the (pixel-wise) appearance of the screen is captured as
hnd
gca
gcf
f = getframe( hnd ); img = f.cdata;
Notes: when capturing a sequence, do not forget to call drawnow before capturing. Also be careful not to obscure the captured window by other GUI content, mouse pointer, etc.
drawnow
mov = avifile( 'my_file.avi' ); mov.compression = 'none'; mov.fps = 25; % or whatever you want % now iterate creation of frames % all frames must have the same size mov = addframe( mov, img ); % end of frame creation mov = close( mov );
Note that video compression (compression different from 'none') usually does not work well, so preferred way is to store raw sequence and compress later.