2020-05-28 20:04:57 -0500 received badge ● Popular Question (source) 2017-03-03 07:39:05 -0500 commented answer Covariant Derivative gives Error, why? (SAGE 7.5.1) Great, I did, it works. 2017-03-02 04:19:05 -0500 received badge ● Scholar (source) 2017-03-02 04:18:17 -0500 commented answer Covariant Derivative gives Error, why? (SAGE 7.5.1) Thanks Eric, now that I know it is a bug, i will for now use an older version of Sage. Many greetings! 2017-03-01 17:08:09 -0500 asked a question Covariant Derivative gives Error, why? (SAGE 7.5.1) This simple code gives an Error: f = function('f') B=Manifold(2,'B',start_index=1) polar. = B.chart(R'R:(0,+oo) Phi:(0,2*pi):\Phi') G = B.riemannian_metric('G') G[1,1]=diff(f(R),R) G[2,2]=f(R)^2 nabla=G.connection() S=B.tensor_field(1,1) S[1,1]=R^(0.5) S[2,2]=R^3 S.display() nabla(S) Error: TypeError: unable to convert R to an integer  This Error doesn't occur either if I avoid the square root in S[1,1]=R^(0.5), for example by writing S[1,1]=R^(0.4) or if I avoid the dependence of the derivative of f in the first entry of the metric, for example by writing G[1,1]=f(R)^2. This Error also doesn't occur in older Sage versions, for example Sage 7.1 Thanks a lot for help!