unable to evaluate m of the n functions to numeric values - Maple Help

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Warning, unable to evaluate m of the n functions to numeric values in the region; see the plotting command's help page to ensure the calling sequence is correct

 Description Note: For users of Maple 15 and earlier versions, this warning occurs when you create a Maple plot without points, curves, or surfaces.  In the warning message, "functions" refers to the functions being plotted (expressed as an algebraic expressions or procedures) and "region" refers to the plotting domain.   Verify that you are using the correct syntax for the plotting command and that the function values are real numbers in the specified region.

Examples

Example 1
In this example, the plot command is used to plot a list of functions.   Note that a warning message is displayed and only one function is graphed.

The warning occurs because the function values for some of the functions in the list are not numeric.

 > $\mathrm{plot}\left(\left[b,x,b+x\right],x=0..1\right)$

Solution:

Assign a value to $b$ before plotting the functions.  Now all three functions are shown on the graph.

 > $b≔3:$
 > $\mathrm{plot}\left(\left[b,x,b+x\right],x=0..1\right)$

Example 2

In this example, the plot command is used to plot a set of functions.  Note that the warning appears and only the first function is graphed.

The warning occurs because the function $g$ is not properly defined; when you simply type the letter $e$, it is interpreted by Maple as a name rather than the natural exponential function.

 > $f:={x}^{2};\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}$$g:=x{e}^{-\frac{1}{2}\cdot x}$
 ${f}{:=}{{x}}^{{2}}$
 ${g}{:=}{x}{}{{e}}^{{-}\frac{{1}}{{2}}{}{x}}$ (2.1)
 > $\mathrm{plot}\left(\left\{f,g\right\},x=-2..2\right)$

Solution:

To define g, you must use the exponential 'e'.  One way to obtain this is to use the ${ⅇ}^{{a}}$ template from the Expression Palette and then replace ${a}$ with $-\frac{1}{2}\cdot x$.  For more information on the exponential 'e', see the exp help page.

 > $f:={x}^{2};\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}\phantom{\rule[-0.0ex]{0.0em}{0.0ex}}$$g:=x{ⅇ}^{-\frac{1}{2}\cdot x}$
 ${f}{:=}{{x}}^{{2}}$
 ${g}{:=}{x}{}{{ⅇ}}^{{-}\frac{{1}}{{2}}{}{x}}$ (2.2)
 > $\mathrm{plot}\left(\left\{f,g\right\},x=-2..2\right)$