title: Visualizing a large matrix in matlab
body: <p>I have a huge sparse matrix (1,000 x 1,000,000) that I cannot load on matlab (not enough RAM).</p>
  
  <p>I want to visualize this matrix to have an idea of its sparsity and of the differences of the values.</p>
  
  <p>Because of the memory constraints, I want to proceed as follows:</p>
  
  <p>1- Divide the matrix into 4 matrices</p>
  
  <p>2- Load each matrix on matlab and visualize it so that the colors give an idea of the values (and of the zeros particularly)</p>
  
  <p>3- "Stick" the 4 images I will get in order to have a global idea for the original matrix</p>
  
  <p>(i) Is it possible to load "part of a matrix" in matlab?</p>
  
  <p>(ii) For the visualization tool, I <a href="https://stackoverflow.com/questions/14575054/how-to-visualize-a-sparse-matrix-in-matlab">read about</a> spy (and daspect). However, this function only enables to visualize the non-zero values indifferently of their scales. Is there a way to add a color code?</p>
  
  <p>(iii) How can I "stick" plots in order to make one?</p>