Warning, expecting only range variable ... in expressions ... to be plotted but found name ... - Maple Programming Help

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Warning,  expecting only range variable ... in expressions ... to be plotted but found name ...

 Description The plot(f,x) calling sequence plots the real function, f, a function of the independent variable, x, over a horizontal real range.   This warning occurs when the expression that you are trying to plot, using the plot(f,x) calling sequence, contains unexpected names.

Examples

Example 1: Parametric plot

In this example, the variable names used as arguments for the real functions to be plotted do not match the variable name given to the range variable.

 > $\mathrm{plot}\left(\left[\mathrm{sin}\left(t\right),\mathrm{cos}\left(t\right),x=0..\mathrm{Pi}\right]\right)$

Solution: Changing one of the variable names to match the other solves this problem. Here, has been changed to $x.$

 > $\mathrm{plot}\left(\left[\mathrm{sin}\left(x\right),\mathrm{cos}\left(x\right),x=0..\mathrm{Pi}\right]\right)$

Example 2: Using e instead of exp

In this example, the letter e has been raised to a variable exponent, instead of using the calling sequence exp(x) to represent the exponential function.

 > $\mathrm{plot}\left({e}^{x}\mathit{,}x\mathit{=}\mathit{0}\mathit{..}\mathit{1}\right)\mathit{;}$

Solution 1: To plot this expression, replace ${e}^{x}$ with exp(x).

 > $\mathrm{plot}\left(\mathrm{exp}\left(x\right)\mathit{,}x\mathit{=}\mathit{0}\mathit{..}\mathit{1}\right)\mathit{;}$

Solution 2: Alternatively, add from the Expression palette:

 > $\mathrm{plot}\left({ⅇ}^{x},x=0..1\right);$

Example 3: Using pi instead of Pi

 > plot(sin(pi*x), x = 1 .. 2);

Solution:  For calculations, use "Pi" instead of "pi".

 > plot(sin(Pi*x), x = 1 .. 2);

Example 4: using i instead of I

Maple uses I to represent one of the square roots of -1. If you want to create a complex expression, you need to use I.

 >

Solution: Use Uppercase "I" instead of lowercase "i".

 >

Example 5: unassigned value

The constant $a$ has not been assigned a value.

 > $\mathrm{plot}\left(a+x,x=1..2\right)$

Solution: Assign a value to $a$

 > $a≔5$
 ${a}{:=}{5}$ (2.1)
 > $\mathrm{plot}\left(a+x,x=1..2\right)$

Example 6:

Similar to Example 5, in the list of expressions to be plotted, the first expression, contains an undefined constant.

 > $\mathrm{plot}\left(\left[x+b,{x}^{2}\right],x=-1..1\right)$

Solution: Assign a value to $b$

 > $b≔7$
 ${b}{:=}{7}$ (2.2)
 > $\mathrm{plot}\left(\left[x+b,{x}^{2}\right],x=-1..1\right)$

Example 7: 3-D plot example with wrong name used in function.

 > $\mathrm{plot3d}\left(\left[\mathrm{sin}\left(z\right),\mathrm{cos}\left(z\right),z+{y}^{2}\right],x=-1..1,y=-1..1\right);$

Solution:

 > $\mathrm{plot3d}\left(\left[\mathrm{sin}\left(x\right),\mathrm{cos}\left(x\right),x+{y}^{2}\right],x=-1..1,y=-1..1\right);$
 >