Radau Solver error: this value must be a vector.

[ptc-6141584]

I get an error with Radau(init, x1, x2, intvls, D) as 'This value must be a vector.' I'm quite sure I made init and D vectors, and x1 x2 intvls ordinary numbers. Please see the attachment and tell me where the problem is. thanks

[Werner_E]

Use the literal index for t.0, not the vector index.

[ptc-6141584]

Thanks, Werner.

That should be one of the problems. But it seems it does not let the solver back to work.

[ptc-6141584]

The other problem is ths function is complex enough for the Radau, the difference between x1 and x2 need to be small enough to allow the solver work.

[AlanStevens]

Having re-written t0 as t.0, you need to rewrite t/t.0 (in both first and last terms of DD) as well, because Mathcad still thinks t is a vector.

When you do this you get the error that the problem is unstable and the step sizes are getting too small.

Are you sure the numerator (above the upper case lambda) in the first term of DD is written correctly?

Alan