This error occurs when an argument that is not of type algebraic is passed to the diff command.

Example 1

In

Solution 1: Use an expression, not function, for the first argument:

Solution 2: The differential operator D can differentiate procedures (including functional operators).  

For users of Maple 2017 and earlier versions:  Previously, this error was generated in the following cases.  As a result of updates made in Maple 2018, these examples no longer result in an error.

Example 2

In the following example, an error is generated when a Vector, $v$, is passed to the diff command.

This is as expected since $v$ is not of type algebraic.

Solution:

Here, we assume that the intention was to differentiate each element of the Vector.  Since each element in the Vector is an algebraic expression, differentiating element-wise corrects the above error.  Specifically, use ~ to differentiate each element of the Vector.  For more information on ~, see the operators/elementwise help page.

Example 3

In the following example, the call to the VectorCalculus package has been omitted.  This results in the top-level diff function being used for the right-hand side values of $\mathrm{r1}$ and $\mathrm{r2}$, rather than VectorCalculus[diff].  Since the top-level diff function does not accept Vectors as arguments, an error occurs.

Solution:

Adding with(VectorCalculus) before the sequence of statements results in VectorCalculus[diff]. This corrects the error.