Question

I am only a novice programmer, and I would like some help with this problem.

I am currently running simulations of particles that interact and move around on a two-dimensional lattice. The data of where the particles are at any point is stored in a two-dimensional array that I use during the simulation itself.After the simulation, I want to be able to visually see where all of the particles end up. Currently, I send the data to MATLAB, and have it literally plot each particle on a figure. This works, and creates “pictures” of my system configuration. However, for large numbers of particles in a large lattice (With dimensions like 600 particles wide by 1200 particles tall), this makes prohibitively slow-processing pictures, that MATLAB and word processing are very slow to deal with, and which uses up a lot of memory and space.

There must be a better way to do this, does anyone have any ideas on better ways to view my system or control the data?

My matlab code works as the following:

%--------------------------------------- Particle Picture
clc; clear all;
particle_file = fopen('ABC_Particles_600X1200T1.txt');
particles = fscanf(particle_file,'%f');
fclose(particle_file);

figure(3);
hold on;
sizex = 600;
sizey = 1200;

for a = 1:1:sizey*sizex
    b = int32(a);
    if particles(a) == 0
        plot(mod(b,sizex)+1,idivide(b,sizex)+1,'c')
    end
    if particles(a) == 1
        plot(mod(b,sizex)+1,idivide(b,sizex)+1,'r')
    end
    if particles(a) == 2
        plot(mod(b,sizex)+1,idivide(b,sizex)+1,'k')
    end
end    
title('Size 600X1200; Time T = 1')
axis([0 sizex 0 sizey])

Answer 1

you can vectorize your code using logical conditions instead of the loop. for example, z=(particles==0) is a vector of 0 and 1‘s, where you get the value 1 where the element of particles=0. This replaces the code:

for a=1:n
     if particles(a) == 0
        z(a)=1
    else
        z(a)=0
    end
end

So, first we reshape particles from a long vector to a matrix:

p=reshape(particles,600,1200);

then we can use logical conditions as before, or similarly, the function find to get the x and y coordinates of the p according to what you wrote

[x0 y0]=find(p==0);
[x1 y1]=find(p==1);
[x2 y2]=find(p==2);

Then we can just plot it:

plot(x0,y0,'c',x1,y1,'r',x2,y2,'k')

by the way, if 0,1,2 are the only values your data have you can skip all this and just use:

imagesc(p)

That will color code your points differently, but you can change the colormap to whatever you want