Here’s my Mathematica visualization of the electric field inside of the sphere from problem 4.10 in Griffiths EM. I left out the constant k from the answer, as it would only scale the vectors and the overall field will look the same. Though I assumed a positive k, if k is negative the field will point radially outward from the origin instead of inward. Of course, the field only looks like this up to r, the radius of the sphere, at which point it becomes 0 everywhere.