You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: volplot.m
    path of file: ./repos/spm/external/fieldtrip/private
    
    the code of the file until where you have to start completion: function [dat] = volplot(x, y, z, dat, sel, cscale)

% VOLPLOT make 2D or 3D plot of volumetric data (e.g. MRI)
% that is defined on a regular orthogonal grid
% 
% volplot(dat, sel) or
% volplot(x, y, z, dat, sel)
% volplot(x, y, z, dat, sel, caxis)
%
% where sel is one of
%   [x, y, z]     intersection through the three orthogonal directions
%   index         linear index of the voxel of interest
%   'min'         intersection at the minimum
%   'max'         intersection at the maximum

    
function
      h = nas;
      break;
    elseif key=='l'
      lpa = [xc yc zc];
    elseif key=='r'
      rpa = [xc yc zc];
    elseif key=='n'
      nas = [xc yc zc];
    elseif key=='x'
      selx= round((xc-0):(xc+0));
      sely= round((yc-0):(yc+0));
      selz= round((zc-0):(zc+0));
      dat(selx,sely,selz) = 0;
    elseif key=='X'
      selx= round((xc-1):(xc+1));
      sely= round((yc-1):(yc+1));
      selz= round((zc-1):(zc+1));
      dat(selx,sely,selz) = 0;
    else         
      % update the view to a new position
      l1 = get(get(gca, 'xlabel'), 'string');
      l2 = get(get(gca, 'ylabel'), 'string');
      switch l1
        case 'x'
          xc = d1;
        case 'y'
          yc = d1;
        case 'z'
          zc = d1;
      end