Question

I’ve got some code, and I’ve been trying to make some minor tweaks to it. It used to use fgets to load in a single character from a line, and use it to colour points in a 3D plot. So it would read

a
p
p
n
c

and then use other data files to assign what x, y, z points to give these. The result is a really pretty 3D plot.

I’ve edited the input file so it reads

0
1
1
0
2
2
0

and I want it to colour numbers the same colour.

This is where I’ve gotten so far with the code:

    function PlotCluster(mcStep)

   clear all

   filename = input('Please enter filename:   ', 's');

   disp('Loading hopping site coordinates ...')
   load x.dat
   load y.dat
   load z.dat
   temp = z;
   z = x;
   x = temp;
   n_sites = length(x);

       disp('Loading hopping site types ...')
   fp = fopen([filename]);
   data = load(filename);  %# Load the data

   % Plot the devices
   % ----------------

   disp('Plotting the sample surface ...')
   figure
   disp('Hello world!')

   ia = data == 0;
   in = data == 1;
   ip = data == 2;
   disp('Hello Again')

   plot3(x(ia),y(ia),z(ia),'b.') %,'MarkerSize',4)
   hold on
   plot3(x(ic),y(ic),z(ic),'b.') %,'MarkerSize',4)
   plot3(x(in),y(in),z(in),'g.') %,'MarkerSize',4)
   plot3(x(ip),y(ip),z(ip),'r.') %,'MarkerSize',4)
   daspect([1 1 1])
   set(gca,'Projection','Perspective')
   set(gca,'FontSize',16)   
   axis tight
   xlabel('z (nm)','FontSize',18)
   ylabel('y (nm)','FontSize',18)
   zlabel('x (nm)','FontSize',18)
   %title(['Metropolis Monte Carlo step ' num2str(mcStep)])

   view([126.5   23])

My issue is I’m getting this error

Index exceeds matrix dimensions.

Error in PlotCluster (line 34)
   plot3(x(ia),y(ia),z(ia),'b.') %,'MarkerSize',4)

And I don’t see why ia would go out of bounds of the x array. Is it to do with changing the fgets to a load statement? It was the only way to get it read the correct numbers in (not 49s and 50s which was very odd.)

The main bits that are sticking me are these lines (where the number used to correspond to ‘a’,’n’,’p’ etc)

   ia = data == 0;
   in = data == 1;
   ip = data == 2;

They look like implied if statements with assignment from data to ia etc. where ia becomes an array. But I’m not sure.

Any help understanding this would be greatly appreciated.

Answer 1

I’ve fixed the issue, I hadn’t updated my input correctly. To clear this up for anyone who comes to this question: ia = data ==0 means ‘Make an array the same size as data, and fill it with 1 or 0 depending on if the logic (data == 0) is true or false’