100 / Chapter 8 Calculating in Mathcad

Error Messages

If Mathcad encounters an error when evaluating an expression, it marks the expression with an error message and highlights the offending name or operator in red.

An error message is visible only when you click on the associated expression, as shown to the right.

Mathcad cannot process an expression containing an error. If the expression is a definition, the variable or function remains undefined. Any expressions that reference that variable become undefined as well.

Online Help Click on an error message and press [F1] for an explanation of the message.

Finding the Source of an Error

When an expression depends upon one or more existing definitions, an error you receive in your expression may actually originate in one of those definitions.

For example, in the figure above, the error appears on the third region, f(0). However, f(x) is based on the definition of g(x). When x is zero, g(x) is the first region that exhibits the error.

You can try to find the source of an error by examining your worksheet, or you can trace the error back through your worksheet. To find the source of an error:

1.Right-click on the region showing the error and choose Trace Error from the menu or click on the region and choose Trace Error from the

Tools menu.

2.Use the buttons in the Trace Error dialog box to navigate through the regions associated with the region showing the error. For example, click “Previous” to step back to the previous dependent region.

3.Or click “First” to jump to the region causing the error.

Error Messages / 101

Fixing Errors

Once you have determined which expression caused the error, edit that expression to fix the error or change the variable definitions that led to the error. Mathcad first recomputes the edited expression and then recomputes any expressions affected by the fixed expression.

Note When you define a function, Mathcad does not try to evaluate it until you subsequently use it in the worksheet, although it does compile and unit-balance it. If there is an error, the use of the function is marked in error, even though the real problem may lie in the definition of the function itself, possibly much earlier in the worksheet. Evaluating the function name and looking at its type signature may help debug the problem.