title: predict value of curve in matlab
body: <p>Suppose I have the following vector of points:</p>
  
  <pre><code>X=[ 0.401   0.398   0.395   0.392   0.388   0.384   0.381   0.377   0.373   0.368   0.364   0.359   0.354   0.349   0.344   0.339   0.334   0.328   0.322   0.316   0.310   0.304   0.297   0.291   0.284   0.277   0.270   0.263   0.256   0.249   0.242   0.234   0.227   0.220   0.212   0.205   0.198   0.190   0.183   0.176   0.169   0.161   0.154   0.147   0.140   0.134   0.127   0.120   0.113   0.107   0.101   0.094   0.088   0.082   0.076   0.070   0.064   0.059   0.053   0.048   0.042   0.037   0.032   0.027   0.022   0.018   0.013   0.009   0.004   0.000   -0.004  -0.008  -0.012  -0.016  -0.019  -0.023  -0.026  -0.030  -0.033  -0.036  -0.039  -0.042  -0.045  -0.048  -0.050  -0.053  -0.055  -0.058  -0.060  -0.062  -0.064  -0.066  -0.068  -0.070  -0.072  -0.074  -0.076  -0.077  -0.079  -0.080];
  
  Y=[0.347    0.362   0.377   0.393   0.409   0.426   0.442   0.459   0.477   0.494   0.512   0.530   0.548   0.567   0.585   0.604   0.622   0.641   0.659   0.678   0.696   0.715   0.733   0.750   0.768   0.785   0.801   0.817   0.833   0.848   0.863   0.876   0.890   0.902   0.914   0.925   0.935   0.945   0.953   0.961   0.969   0.975   0.981   0.986   0.990   0.993   0.996   0.998   0.999   1.000   1.000   0.999   0.998   0.996   0.994   0.991   0.988   0.984   0.979   0.974   0.969   0.963   0.957   0.951   0.944   0.937   0.930   0.922   0.914   0.906   0.898   0.889   0.881   0.872   0.863   0.855   0.846   0.837   0.827   0.818   0.809   0.800   0.791   0.782   0.773   0.764   0.755   0.747   0.738   0.729   0.721   0.712   0.704   0.696   0.688   0.680   0.672   0.664   0.656   0.649];
  </code></pre>
  
  <p>When I plot the points <code>X</code> and <code>Y</code>, this is what I get:</p>
  
  <p><img src="https://i.stack.imgur.com/10WKq.jpg" alt=""></p>
  
  <p>I want to calculate the value of 'Width' of the curve <code>W</code>.  How can I do that?</p>