* Adding title kwarg for plotter class

* Create tutorial for Fourier Feature Embedding
* Update doc for tutorials

pina/model/layers/embedding.py

@@ -235,7 +235,7 @@ class FourierFeatureEmbedding(torch.nn.Module):
                         size = (input_dimension,
                                 output_dimension // 2),
                         requires_grad = False
-                                )
+                                ) * self.sigma
 
     def forward(self, x):
         """
@@ -248,7 +248,7 @@ class FourierFeatureEmbedding(torch.nn.Module):
         # compute random matrix multiplication
         out = torch.mm(x, self._matrix)
         # return embedding
-        return torch.cat([torch.cos(out), torch.sin(out)], dim=-1)
+        return torch.cat([torch.cos(2*torch.pi*out), torch.sin(2*torch.pi*out)], dim=-1)
     
 
     @property

pina/plotter.py

@@ -168,6 +168,7 @@ class Plotter:
         method="contourf",
         res=256,
         filename=None,
+        title=None,
         **kwargs,
     ):
         """
@@ -186,6 +187,8 @@ class Plotter:
             Default is 'contourf'.
         :param int res: The resolution, aka the number of points used for
             plotting in each axis. Default is 256.
+        :param str title: The title for the plot. If None, the plot
+            is shown without a title. Default is None.
         :param str filename: The file name to save the plot. If None, the plot
             is shown using the setted matplotlib frontend. Default is None.
         """
@@ -241,6 +244,9 @@ class Plotter:
             )
 
         plt.tight_layout()
+        if title is not None:
+            plt.title(title)
+            
         if filename:
             plt.savefig(filename)
             plt.close()