Page 4: Plotting, Data Visualization, and File I/O

4. Plotting, Data Visualization, and File I/O

MATLAB is renowned for its excellent plotting capabilities, allowing you to visualize data effectively. It also provides robust tools for managing data persistence through file input/output.

4.1. 2D and 3D Plotting Basics

Create various types of plots with simple commands:

• 2D Plots: plot, scatter, bar.

  x = 0:0.1:2*pi;
  y = sin(x);
  plot(x, y, 'b--o'); % Blue dashed line with circles
  xlabel('X-axis');
  ylabel('Y-axis');
  title('Sine Wave Plot');
  legend('sin(x)');
  grid on;
  

• Multiple Plots: Use hold on to add more data to an existing plot.

  hold on;
  plot(x, cos(x), 'r:x'); % Red dotted line with 'x' markers
  hold off;
  

• 3D Plots: plot3, surf, mesh.

  [X,Y] = meshgrid(-2:.2:2);
  Z = X .* exp(-X.^2 - Y.^2);
  surf(X,Y,Z);
  colorbar;
  

4.2. File Input/Output

MATLAB offers functions to read and write data from/to files.

• MAT-files: MATLAB\'s native format for saving/loading Workspace variables.

  data = [1 2 3; 4 5 6];
  save('mydata.mat', 'data'); % Saves 'data' variable to mydata.mat
  clear data;
  load('mydata.mat'); % Loads 'data' back into Workspace
  

• CSV files: Common format for tabular data.

  writematrix(data, 'output.csv');
  loaded_data = readmatrix('output.csv');
  

• Text files: For custom text file formats.

  fileID = fopen('log.txt', 'w'); % Open for writing
  fprintf(fileID, 'Processing complete at %s\n', datestr(now));
  fclose(fileID);
  

Key Concept: Effective visualization makes complex data understandable, and reliable file I/O ensures your data is persistent and exchangeable.