The transform is \hat{x} = L(x-R)/(L-R).

In 1D, my code to save the data in the initial (not transformed) mesh is:

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# mesh on which I solve the equations (\hat{x})
mesh_transformed = mesh.coordinates.vector().get_local()  

# back to the initial mesh (applying the inverse transform) (x)

mesh.coordinates.vector().set_local(mesh_transformed*(L-R)/L + R)

# save data on the initial mesh
save_h << h

# Back to the transformed mesh to solve the WF (\hat{x})

mesh.coordinates.vector().set_local(mesh_transformed)

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This works well in 1D. However, I would like to extend my model in 2D, where the transform is still only in x. Therefore, I would like to apply the previous manipulation to the x coordinate only, and not on the 2D mesh. The previous code changes both x and y. 

How can I change only x ?

Thanks,

Floriane