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Well, I would say that this is caused by a somewhat strange operation that you are asking for. When you write

v = E.vector_field([r_1,0,0], frame=spherf, chart=cart)
v.apply_map(lambda c:c.subs(ph==ph_1, th==th_1))

you are initializing the vector field with components in the frame spherf (orthonormal frame associated with spherical coordinates), while the second line asks for an apply_map in the default frame, which is cartf. But at this stage, such components are not known. Such a substitution is thus not very meaningful. If you add v.display() before v.apply_map, as in your second example, this triggers the computations of the components with respect to cartf, so that the substitution becomes meaningful. If you want to stick to the first example, then you enforce apply_map to act on the components w.r.t spherf, by adding the argument frame=spherf:

v = E.vector_field([r_1,0,0], frame=spherf, chart=cart)
v.apply_map(lambda c:c.subs(ph==ph_1, th==th_1), frame=spherf)

Then everything is OK.

Well, I would say that this is caused by a somewhat strange operation that you are asking for. When you write

v = E.vector_field([r_1,0,0], frame=spherf, chart=cart)
v.apply_map(lambda c:c.subs(ph==ph_1, th==th_1))

you are initializing the vector field with components in the frame spherf (orthonormal frame associated with spherical coordinates), while the second line asks for an apply_map in the default frame, which is cartf. But at this stage, such components are not known. Such a substitution is thus not very meaningful. If you add v.display() before v.apply_map, as in your second example, this triggers the computations computation of the components with respect to cartf, so that the substitution becomes meaningful. If you want to stick to the first example, then you enforce apply_map to act on the components w.r.t spherf, by adding the argument frame=spherf:

v = E.vector_field([r_1,0,0], frame=spherf, chart=cart)
v.apply_map(lambda c:c.subs(ph==ph_1, th==th_1), frame=spherf)

Then everything is OK.

Well, I would say that this is caused by a somewhat strange operation that you are asking for. When you write

v = E.vector_field([r_1,0,0], frame=spherf, chart=cart)
v.apply_map(lambda c:c.subs(ph==ph_1, th==th_1))

you are initializing the vector field with components in the frame spherf (orthonormal frame associated with spherical coordinates), while the second line asks for an apply_map in the default frame, which is cartf. But at this stage, such components are not known. Such a substitution is thus not very meaningful. If you add v.display() before v.apply_map, as in your second example, this triggers the computation of the components with respect to cartf, so that the substitution becomes meaningful. If you want to stick to the first example, then you should enforce apply_map to act on the components w.r.t spherf, by adding the argument frame=spherf:

v = E.vector_field([r_1,0,0], frame=spherf, chart=cart)
v.apply_map(lambda c:c.subs(ph==ph_1, th==th_1), frame=spherf)

Then everything is OK.