# Element Stiffness Matrix#

The stiffness matrices are integrated numerically where the number of
integration points is fixed for each element type by the parameter `npts`

.
The element has a number of dimensions defined by `ndim`

. Suppose we have
`nel`

2-D elements (`ndim=2`

) for which the stiffness matrix has to be
calculated, the following should be defined:

\[j = [{j11}_1, {j12}_1, {j21}_1, {j22}_1, ...,
{j11}_{nel}, {j12}_{nel}, {j21}_{nel}, {j22}_{nel}]\]