Re: [Scilab-users] function find()
Thank you all for your suggestions concerning pair-wise distances. The motivation behind my question is that I am writing a simplistic molecular dynamics program, where hard disks move freely inside a plane region, except when colliding with boudaries or with other disks. I hoped that my program could be as fast as the beautiful Python program of Jake Vanderplas (http://jakevdp.github.com) but, up to now, the Python code is still significantly faster. JP Grive ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] function find()
Hello, >// initialisation >diam = 0.2; >nd = 10; >etat = (rand(nd,2) -0.5)*4; >distance = zeros(nd,nd); >//compute distance matrix >for i = 1:(nd-1) > for j = (i+1):nd > distance(i,j) = > sqrt((etat(i,1)-etat(j,1))**2+(etat(i,2)-etat(j,2)**2)); > end >end You may do without explicit nested loops: [X,Y] = meshgrid(etat(:,1), etat(:,2)); distance = sqrt((X-X.').^2 + (Y-Y.').^2) Samuel ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] function find()
Le 27/05/2014 14:45, Dang, Christophe a écrit : Hello, Appart from the parenthetis error pointed out by Pierre-Aimé, something imho a bit more efficient: distance(i,j) = norm([etat(i, :) - etat(j, :)]) Best regards Thank you Pierre-Aimé and Daniel for pointing ou this simple error. JP Grivet ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] function find()
Hello, Appart from the parenthetis error pointed out by Pierre-Aimé, something imho a bit more efficient: distance(i,j) = norm([etat(i, :) - etat(j, :)]) Best regards -- Christophe Dang Ngoc Chan Mechanical calculation engineer __ This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error), please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden. __ ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] function find()
Hi, You are computing "operator<" over complex number (which is not defined) because your distance matrix has an error Try with this change distance(i,j) = sqrt((etat(i,1)-etat(j,1))**2+(etat(i,2)-etat(j,2)**2)); => distance(i,j) = sqrt((etat(i,1)-etat(j,1))**2+(etat(i,2)-etat(j,2))**2); Full script: // initialisation diam = 0.2; nd = 10; etat = (rand(nd,2) -0.5)*4; distance = zeros(nd,nd); //compute distance matrix for i = 1:(nd-1) for j = (i+1):nd distance(i,j) = sqrt((etat(i,1)-etat(j,1))**2+(etat(i,2)-etat(j,2))**2); end end //find close pairs [li,lj] = find(distance Hello, While trying to compute pairwise distances between random points, I have come across a behavior of function find() that I don't understand. I do the following: // initialisation diam = 0.2; nd = 10; etat = (rand(nd,2) -0.5)*4; distance = zeros(nd,nd); //compute distance matrix for i = 1:(nd-1) for j = (i+1):nd distance(i,j) = sqrt((etat(i,1)-etat(j,1))**2+(etat(i,2)-etat(j,2)**2)); end end //find close pairs [li,lj] = find(distanceWith both Scilab 5.4.1 and Scilab 5.5, the last line raises the error message: !--error 144 Opération non définie pour les opérandes données. I will be grateful to anybody who spots my error. Thank your for your time, JP Grivet ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users -- Pierre-Aimé Agnel Development Team --- Scilab Enterprises 143bis rue Yves Le Coz - 78000 Versailles, France Phone: +33.1.80.77.04.68 http://www.scilab-enterprises.com ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
[Scilab-users] function find()
Hello, While trying to compute pairwise distances between random points, I have come across a behavior of function find() that I don't understand. I do the following: // initialisation diam = 0.2; nd = 10; etat = (rand(nd,2) -0.5)*4; distance = zeros(nd,nd); //compute distance matrix for i = 1:(nd-1) for j = (i+1):nd distance(i,j) = sqrt((etat(i,1)-etat(j,1))**2+(etat(i,2)-etat(j,2)**2)); end end //find close pairs [li,lj] = find(distanceWith both Scilab 5.4.1 and Scilab 5.5, the last line raises the error message: !--error 144 Opération non définie pour les opérandes données. I will be grateful to anybody who spots my error. Thank your for your time, JP Grivet ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
