http://www.k-wave.org/forum/topic/how-to-assign-the-properties-of-medium-ball-in-multilayers Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 02:34:06 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/how-to-assign-the-properties-of-medium-ball-in-multilayers#post-3700 Thu, 06 Jun 2013 12:00:59 +0000 Bradley Treeby 3700@http://www.k-wave.org/forum/ <p>Hi Maktjik,</p> <p>The answer is in the error message - you are trying to index a matrix using another matrix defined in double precision. Your indices must be either real positive integers or logicals, i.e., one of the following</p> <pre><code>medium.sound_speed(ball == 1) = c_ball; medium.sound_speed(find(ball == 1)) = c_ball; medium.sound_speed(logical(ball)) = c_ball;</code></pre> <p>See <a href="http://www.mathworks.co.uk/help/matlab/math/matrix-indexing.html">here</a> if you need some more information.</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/how-to-assign-the-properties-of-medium-ball-in-multilayers#post-3699 Thu, 06 Jun 2013 11:53:15 +0000 maktjik 3699@http://www.k-wave.org/forum/ <p>Hi All,</p> <p>I would like to define 4 layers medium and a ball within the layers.</p> <p>I could assign the properties of the layers, but how to assign the properties of the ball?</p> <p>Here is my code:</p> <pre><code>% define a random distribution of scatterers for the medium background_map_mean = 1; background_map_std = 0.008; % define the thicknesses of layer phantom in x direction d_layer_1 = 5.4e-3; % [m] d_layer_2 = 4.9e-3; % [m] d_layer_3 = 4.4e-3; % [m] d_layer_4 = 6.3e-3; % [m] % define the thicknesses of layer phantom in x direction position_x1 = 1:round(Nx*(d_layer_1/x)); position_x2 = round(Nx*(d_layer_1/x))+1:round(Nx*((d_layer_1+d_layer_2)/x)); position_x3 = round(Nx*((d_layer_1+d_layer_2)/x))+1:round(Nx*((d_layer_1+d_layer_2+d_layer_3)/x)); position_x4 = round(Nx*((d_layer_1+d_layer_2+d_layer_3)/x))+1:round(Nx*((d_layer_1+d_layer_2+d_layer_3+d_layer_4)/x)); % define the width of phantom in y and z direction width_y = 29e-3; % width_phantom_in y direction [grid points]*dy = [m] width_z = 35e-3; % width_phantom_in z direction [grid points]*dz = [m] % define position of each layer in y and z direction position_y = round(Ny*(((y-width_y)/2)/y))+1:round(Ny*(y-(y-width_y)/2)/y); position_z = round(Nz*(((z-width_z)/2)/z))+1:round(Nz*(z-(z-width_z)/2)/z); % define the dimension of each layer (equal to its background map) width_backgroundmap_layer_1 = [round(Nx*(d_layer_1/x)), round(Ny*(y-(y-width_y)/2)/y)-round(Ny*(((y-width_y)/2)/y)), round(Nz*(z-(z-width_z)/2)/z)-round(Nz*(((z-width_z)/2)/z))]; width_backgroundmap_layer_2 = [round(Nx*((d_layer_1+d_layer_2)/x))-(round(Nx*(d_layer_1/x))), round(Ny*(y-(y-width_y)/2)/y)-round(Ny*(((y-width_y)/2)/y)), round(Nz*(z-(z-width_z)/2)/z)-round(Nz*(((z-width_z)/2)/z))]; width_backgroundmap_layer_3 = [round(Nx*((d_layer_1+d_layer_2+d_layer_3)/x))-(round(Nx*((d_layer_1+d_layer_2)/x))), round(Ny*(y-(y-width_y)/2)/y)-round(Ny*(((y-width_y)/2)/y)), round(Nz*(z-(z-width_z)/2)/z)-round(Nz*(((z-width_z)/2)/z))]; width_backgroundmap_layer_4 = [round(Nx*((d_layer_1+d_layer_2+d_layer_3+d_layer_4)/x))-(round(Nx*((d_layer_1+d_layer_2+d_layer_3)/x))), round(Ny*(y-(y-width_y)/2)/y)-round(Ny*(((y-width_y)/2)/y)), round(Nz*(z-(z-width_z)/2)/z)-round(Nz*(((z-width_z)/2)/z))]; % % define the properties of the propagation medium % % water medium.sound_speed = c0*ones(Nx, Ny, Nz); % [m/s] medium.density = rho0*ones(Nx, Ny, Nz); % [kg/m^3] % layer_1 background_map_layer_1 = background_map_mean + background_map_std*randn(width_backgroundmap_layer_1); medium.sound_speed(position_x1, position_y, position_z) = 1520.*background_map_layer_1; % [m/s] medium.density(position_x1, position_y, position_z) = 1281.*background_map_layer_1; % [kg/m^3] % layer_2 background_map_layer_2 = background_map_mean + background_map_std*randn(width_backgroundmap_layer_2); medium.sound_speed(position_x2, position_y, position_z) = 1218.*background_map_layer_2; % [m/s] medium.density(position_x2, position_y, position_z) = 1510.*background_map_layer_2; % [kg/m^3] % layer_3 background_map_layer_3 = background_map_mean + background_map_std*randn(width_backgroundmap_layer_3); medium.sound_speed(position_x3, position_y, position_z) = 1325.*background_map_layer_3; % [m/s] medium.density(position_x3, position_y, position_z) = 1643.*background_map_layer_3; % [kg/m^3] % layer_4 background_map_layer_4 = background_map_mean + background_map_std*randn(width_backgroundmap_layer_4); medium.sound_speed(position_x4, position_y, position_z) = 1429.*background_map_layer_4; % [m/s] medium.density(position_x4, position_y, position_z) = 1684.*background_map_layer_4; % [kg/m^3] % define a ball for a highly scattering region radius = 4e-3; % [m] ball = makeBall(Nx, Ny, Nz, Nx/2, Ny/2, Nz/2, round(radius/dx)); % define properties of the ball c_ball = 3000; rho_ball = 2500; % assign region of the ball medium.sound_speed(ball) = c_ball; % [m/s] medium.density(ball) = rho_ball; % [kg/m^3]</code></pre> <p>I got an error message 'Subscript indices must either be real positive integers or logicals' for the last 2 lines.</p> <p>Do you have a suggestion how to do it properly?</p> <p>Many thanks.</p> <p>Maktjik </p>