creating subplot from function

I have some code, generally looks like this:

x='dr_0.01.txt';
foo(x);

function y = foo(fname)

Do stuff 

end

Ultimately, the function creates a figure. How can I load in other files with the x variable, run foo(x), and put each figure created from each call to function f into a subplot that is 2x2? So I want to load in 4 files, and call the function on all 4 files. Then create a subplot that contains all 4.

Answer 1

[Chad Greene]

Looks like instead of x you meant to call that variable fname? If so, something like this:

fname = {'fname1.txt','fname2.txt','fname3.txt','fname4.txt'}; 

function y = foo(fname) 
  % Load and plot each dataset: 
  for k = 1:length(fname) 
     D = importdata(fname{k}); 
     subplot(2,2,k) 
     y(k) = plot(D(:,1),D(:,2))
  end
end

[Benjamin]

Any reason why this code does not produce all 4 graphs on the subplot? It just produces the one at the top left.

fname = {'dr_0.01.txt','dr_0.005.txt','dr_0.001.txt','dr_0.0001.txt'}; 
delimiterIn = ' ';
headerlinesIn = 5;
foo(fname);
function y = foo(fname) 
  % Load and plot each dataset: 
  for k = 1:length(fname) 
     matrix = importdata(fname{k}); 
     A = matrix.data;

      %Define the number of distinct isotherms
         temp_ids = sum(A(:) == 0.2);

      %Define the number of density points sampled
      density_ids = length(A)/temp_ids;

      %Grab density matrix
      density = A((1:density_ids),1);

      %Grab temperature matrix
      pressure = A(:,3);

      %Reshape pressure matrix so it has one column for each temperature
      %(isotherm), rather than just a single long column
      pressure = reshape(pressure,[density_ids,temp_ids]);

          %Differentiate 
      [~,dPdD] = gradient(pressure, mean(diff(density)));

      [~,ddPddD] = gradient(dPdD, mean(diff(density)));
      subplot(2,2,k)
      y(k) = plot(density, ddPddD);

      grid on;
      ylim([-0.2 0.4])
      xlim([0.4 0.8])
      xlabel('\rho (g/cm^3)');
      ylabel('\partial^2p/\partial\rho^2')

    end
  end

It outputs a subplot, but only the top left graph shows up. Note that density is an a single column array and ddPddD is several columns and rows. It gives this error:

Unable to perform assignment because the indices on the left side are not compatible with the size of the right side.

Error in prac>foo (line 40)
    y(k) = plot(density, ddPddD);

Error in prac (line 9)
foo(fname);