I am trying to create a normal random moving point for each individual point in a 3D scatter point. How do I go about to do this?

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sui zhi lau 2020-4-7

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https://ww2.mathworks.cn/matlabcentral/answers/515956-i-am-trying-to-create-a-normal-random-moving-point-for-each-individual-point-in-a-3d-scatter-point

评论： darova 2020-4-28

I am trying to replicate the random movements (gaussian distribution) found in particles and to do that, I have already made a moving plot (in a normal random distribution) but I am trying to have a maybe 5 by 5 number of points with each point having its on random moving point.

Code attached are the moving plot and the scatter plot

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darova 2020-4-7

Can you be more specific? Here is the result of one of your script

How do you want it to look like?

sui zhi lau 2020-4-7

Hi Darova,

Thanks for replying! For the moving plot, this would be counted as the movement for one 'particle'. So would it be possible for multiple points to be moving cocurrently in the same plot.

So for the no magnetic field code, I would like to have each point's arrow moving randomly. so it would be:

But with the same moving plot for each points on this plot.

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Answer 1

darova 2020-4-7

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/515956-i-am-trying-to-create-a-normal-random-moving-point-for-each-individual-point-in-a-3d-scatter-point#answer_424582

在 MATLAB Online 中打开

What about this?

n = 5;
[X,Y] = meshgrid(1:n);              % create mesh
T = 180*rand(n)-90;                 % initial angles
cla
plot(X(:),Y(:),'ob')                % plot starting points
hold on
for i = 1:30
    T = T + rand(n)*90 - 45;        % increase/decrease angle
    X = X + 0.05*cosd(T);           % increase/decrease X coordinate
    Y = Y + 0.05*sind(T);           % increase/decrease Y coordinate
    plot(X(:),Y(:),'.r')            % plot new coordinates
    pause(0.1)
end
hold off

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sui zhi lau 2020-4-24

编辑：sui zhi lau 2020-4-24

在 MATLAB Online 中打开

hi darova,

This is a long shot but would it be posisble to add certain range of values to converge to the centre of the plot but it does not show any changes.

I have attached my code and a rough guide as to how I would like my point to converge to the centre with arrows.

I would like the points at the red box to change from random moving points to points moving towards the centre (black box)

I have attached my MATLAB file and hope that my explanation of my problem makes sense.

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
%%
scale = 0.5;
k = -1;
y = 1;
nmesh = 5;
niter = 40; %no. of jumps
s = 35.3;% size of particle -> diameter = 45 nm , area of circle = 35.343 nm^2 
[X,Y] = meshgrid((-nmesh+1):nmesh-1); % create mesh of -X -> X, -Y -> Y
X = 10*X;
Y = 10*Y;
dx = normrnd(0,1,[(size(X,1))^2 niter]); %
dy = normrnd(0,1,[(size(X,1))^2 niter]);
MagF=X/2;
countmax = size(X,1);
cla
%plot(X(:),Y(:),'ob')% plot starting points
%%
grid off
hold on
%plot(X,Y,'k')                % plot grid
%plot(X',Y','k')
%%
for i = 1:niter-1
    X1 = X(:) + dx(:,i);
    Y1 = Y(:) + dy(:,i);
    if (-MagF < X < MagF) 
            %U = X - X;
            %V = Y - Y;
         U = k.* ones(1,length(X))
         V = zeros(1,countmax)
        u = U;
        v = V;
        u(1:(countmax-1))=0
        v(1:(countmax-1))=0
        q1 = quiver(X1,Y1,u,v)
        q1.LineWidth = s;
        hold on
        grid on
        %%
        else
   % q = quiver(X1, Y1, (dx(:,i+1)-dx(:,i))*1.1, 1.1*(dy(:,i+1)-dy(:,i)),scale)
    q.ShowArrowHead = 'off';
    q.LineWidth = 3;
%     plot([X(:) X(:)]'+[dx(:,i+1) dx(:,i)]', ...
%          [Y(:) Y(:)]'+[dy(:,i+1) dy(:,i)]','.-r')
    pause(0.5)
    %% percentage readings  
    Image = getframe();
    K = sum(sum(rgb2gray(Image.cdata)==255));                                 
    percentageofwhite(y) = K/numel(rgb2gray(Image.cdata))*100;
    delete(findall(gcf,'type','text'))
    txt=text(0.0,0.95,sprintf('White Space = %0.3f%%',percentageofwhite(y)),'Units','normalized');
    y=y+1;
    xlim([-nmesh^2 nmesh^2])
    ylim([-nmesh^2 nmesh^2])
    end
end
hold off

sui zhi lau 2020-4-26

在 MATLAB Online 中打开

Sorry but how am i supposed to put this in ?

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
%%
scale = 0.5;
y = 1;
nmesh = 8;
niter = 40;
[X,Y] = meshgrid(0:nmesh-1) % create mesh
X = 10*X;
Y = 10*Y;
dx = normrnd(0,1,[nmesh^2 niter]);
dy = normrnd(0,1,[nmesh^2 niter]);
cla
%plot(X(:),Y(:),'ob')% plot starting points
%%
grid off
hold on
%plot(X,Y,'k')                % plot grid
%plot(X',Y','k')
%%
for i = 1:niter-1
    X1 = X(:) + dx(:,i);
    Y1 = Y(:) + dy(:,i);
    q = quiver(X1, Y1, (dx(:,i+1)-dx(:,i)), (dy(:,i+1)-dy(:,i)),scale)
    q.ShowArrowHead = 'on'
    q.LineWidth = 3
%     plot([X(:) X(:)]'+[dx(:,i+1) dx(:,i)]', ...
%          [Y(:) Y(:)]'+[dy(:,i+1) dy(:,i)]','.-r')
    pause(0.5)
    %% percentage readings  
    Image = getframe();
    K = sum(sum(rgb2gray(Image.cdata)==255));                                 
    percentageofwhite(y) = K/numel(rgb2gray(Image.cdata))*100;
    delete(findall(gcf,'type','text'))
    txt=text(0.0,0.95,sprintf('White Space = %0.3f%%',percentageofwhite(y)),'Units','normalized');
    y=y+1;
    xlim([-nmesh nmesh^2])
    ylim([-nmesh nmesh^2])
end
hold off

sui zhi lau 2020-4-26

在 MATLAB Online 中打开

ya i define but i am still getting only the random moving ones ?

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
%%
scale = 0.5;
y = 1;
nmesh = 8;
niter = 40;
[X,Y] = meshgrid(0:nmesh-1) % create mesh
X = 10*X;
Y = 10*Y;
dx = normrnd(0,1,[nmesh^2 niter]);
dy = normrnd(0,1,[nmesh^2 niter]);
cla
%plot(X(:),Y(:),'ob')% plot starting points
%%
grid off
hold on
%plot(X,Y,'k')                % plot grid
%plot(X',Y','k')
%%
c0 = nmesh;                         % center of magnetic field
for i = 1:size(dx,1)
    [ii,jj] = ind2sub(size(X),i);   % row and column of force
    n = hypot(ii-c0,jj-c0);         % distance to point
    if n < 2.1                      % radius of magnetic force
        dx(i,:) = -cumsum(dx(i,:)*0+(jj-c0)/n);  % cosinus
        dy(i,:) = -cumsum(dy(i,:)*0+(ii-c0)/n);  % sinus
    end
        plot([X(:) X(:)]'+[dx(:,i+1) dx(:,i)]', ...
        [Y(:) Y(:)]'+[dy(:,i+1) dy(:,i)]','.-r')
    %% percentage readings  
    Image = getframe();
    K = sum(sum(rgb2gray(Image.cdata)==255));                                 
    percentageofwhite(y) = K/numel(rgb2gray(Image.cdata))*100;
    delete(findall(gcf,'type','text'))
    txt=text(0.0,0.95,sprintf('White Space = %0.3f%%',percentageofwhite(y)),'Units','normalized');
    y=y+1;
    xlim([-nmesh nmesh^2])
    ylim([-nmesh nmesh^2])
end
hold off

sui zhi lau 2020-4-27

编辑：darova 2020-4-27

在 MATLAB Online 中打开

Im sorry Darova if i asked something ignorant. I only picked up MATLAB just late last year and I am still getting confused since most of what i did are self-learned.

Anyways, if possible, would you mind vetting through my 3D plot? I tried to change it up but I cant get it to run

Sorry for the trouble

clc;        % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;      % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
niter = 40; % no. of jumps
scale = 0.5; 
y = 1; % white percentage
%% range of results
d = 1;
nmesh = 4; %range 
[X,Y,Z] = meshgrid((-nmesh+1):nmesh-1); % create mesh
X = X * d;
Y = Y * d;
Z = Z * d;
%% random direction for X,Y,Z
dx = normrnd(0,1,[(size(X,1))^3 niter]);
dy = normrnd(0,1,[(size(X,1))^3 niter]);
dz = normrnd(0,1,[(size(X,1))^3 niter]);
%% Magnetised particles
c0 = nmesh;                         % center of magnetic field
for i = 1:size(dx,1)
    [ii,jj] = ind2sub(size(X),i);   % row and column of force
    n = hypot(ii-c0,jj-c0);         % distance to point
    if n < 3.5                      % radius of magnetic force
        dx(i,:) = -cumsum(dx(i,:)*0+(jj-c0)/n);  % cosinus
        dy(i,:) = -cumsum(dy(i,:)*0+(ii-c0)/n);  % sinus
        dz(i,:) = -cumsum(dz(i,:)*0+(ii-c0)/n);
    end
end
cla
%plot3(X(:),Y(:),Z(:),'ob')         % plot starting points
hold on
%plot(X,Y,'k')                % plot grid
%plot(X',Y','k')
%% For Loop to plot graph
for i = 1:niter-1
    X1 = X(:) + dx(:,i);
    Y1 = Y(:) + dy(:,i);
    Z1 = Z(:) + dz(:,i);
    %q = quiver3(X1, Y1, Z1, dx(:,i+1)-dx(:,i), dy(:,i+1)-dy(:,i),dz(:,i+1)-dz(:,i))
    %q.LineWidth = s;
    %q.ShowArrowHead = 'off';
     plot3([X(:) X(:)]'+[dx(:,i+1) dx(:,i)]', ...
         [Y(:) Y(:)]'+[dy(:,i+1) dy(:,i)]',...
         [Z(:) Z(:)]'+[dz(:,i+1) dz(:,i)]','.-r')
    pause(0.05)
    %% percentage readings  
    Image = getframe();
    K = sum(sum(rgb2gray(Image.cdata)==255));                                 
    percentageofwhite(y) = K/numel(rgb2gray(Image.cdata))*100;
    delete(findall(gcf,'type','text'))
    txt=text(0.0,0.95,sprintf('White Space = %0.3f%%',percentageofwhite(y)),'Units','normalized');
    y=y+1;
    xlim([-5*d d*5])
    ylim([-5*d d*5])
end
hold off
xlabel('My x label')
ylabel('My y label')
zlabel('My z label')
rotate3d on

sui zhi lau 2020-4-28

在 MATLAB Online 中打开

I tried it and it showed this

I dont see the random movements or the coverging to the centre.

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
niter = 40; % no. of jumps
scale = 0.5; 
y = 1; % white percentage
%% range of results
d = 1;
nmesh = 4; %range 
[X,Y,Z] = meshgrid((-nmesh+1):nmesh-1); % create mesh
X = X * d;
Y = Y * d;
Z = Z * d;
%% random direction for X,Y,Z
dx = normrnd(0,1,[(size(X,1))^3 niter]);
dy = normrnd(0,1,[(size(X,1))^3 niter]);
dz = normrnd(0,1,[(size(X,1))^3 niter]);
%% Magnetised particles
c0 = nmesh;                         % center of magnetic field
for i = 1:size(dx,1)
    [ii,jj,kk] = ind2sub(size(X),i);   % row and column of force
    n = pdist2([ii jj kk],[c0 c0 c0]);         % distance to point
    if n < 2.1                      % radius of magnetic force
        dx(i,:) = -cumsum(dx(i,:)*0+(ii-c0)/n);  % cosinus
        dy(i,:) = -cumsum(dy(i,:)*0+(jj-c0)/n);  % sinus
        dz(i,:) = -cumsum(dz(i,:)*0+(kk-c0)/n);
    end
end
cla
%plot3(X(:),Y(:),Z(:),'ob')         % plot starting points
hold on
%plot(X,Y,'k')                % plot grid
%plot(X',Y','k')
%% For Loop to plot graph
for i = 1:niter-1
    X1 = X(:) + dx(:,i);
    Y1 = Y(:) + dy(:,i);
    Z1 = Z(:) + dz(:,i);
    %q = quiver3(X1, Y1, Z1, dx(:,i+1)-dx(:,i), dy(:,i+1)-dy(:,i),dz(:,i+1)-dz(:,i))
    %q.LineWidth = s;
    %q.ShowArrowHead = 'off';
     plot3([X(:) X(:)]'+[dx(:,i+1) dx(:,i)]', ...
         [Y(:) Y(:)]'+[dy(:,i+1) dy(:,i)]',...
         [Z(:) Z(:)]'+[dz(:,i+1) dz(:,i)]','.-r')
    pause(0.001)
    %% percentage readings  
    Image = getframe();
    K = sum(sum(rgb2gray(Image.cdata)==255));                                 
    percentageofwhite(y) = K/numel(rgb2gray(Image.cdata))*100;
    delete(findall(gcf,'type','text'))
    txt=text(0.0,0.95,sprintf('White Space = %0.3f%%',percentageofwhite(y)),'Units','normalized');
    y=y+1;
    xlim([-5*d d*5])
    ylim([-5*d d*5])
end
hold off
xlabel('My x label')
ylabel('My y label')
zlabel('My z label')
rotate3d on

darova 2020-4-28

Please see this

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I am trying to create a normal random moving point for each individual point in a 3D scatter point. How do I go about to do this?

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I am trying to create a normal random moving point for each individual point in a 3D scatter point. How do I go about to do this?

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