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`Function`

, `XFunction`

, `YFunction`

, `ZFunction`

Function expression or procedure

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`Function` , `XFunction` , `YFunction` , `ZFunction` | Mandatory | MuPAD^{®} expression |

`Function`

, `XFunction`

, `YFunction`

, `ZFunction`

correspond
to function expressions or procedures in various plot objects given
by a mathematical function.

The attribute `Function`

is used for graphs
of functions in 2D and 3D, implicit plots, conformal plots etc. which
are characterized by a single function.

The attributes `XFunction`

etc. refer to the
parametrization of the *x*, *y* or *z*-coordinate
of parametrized curves and surfaces. In vector field plots they correspond
to the components of the vector field.

When defining a graphical primitive such as a function plot,
the mathematical expression defining the function is passed directly
to the plot routine generating this object. E.g., one calls ```
plot::Function2d(x*sin(x),
x = -5 .. 5)
```

to define the graph of *f*(*x*)
= *x* *sin*(*x*).
Internally, the attribute `Function = x*sin(x)`

is
associated with the graphical object.

Wherever function expressions are expected, also `piecewise`

objects or
MuPAD procedures can be used. E.g.,
the calls `plot::Function2d(sin(x), x = 0..PI)`

and `plot::Function2d(x -> sin(x), x = 0..PI)`

are equivalent and associate
the attributes `Function = sin(x)`

or ```
Function
= x -> sin(x)
```

, respectively, with the plot objects.

We define an object of type `plot::Function2d`

representing
the graph of *f*(*x*)
= *x* *sin*(*x*):

f := plot::Function2d(x*sin(x), x = -4 .. 4): plot(f)

Internally, the expression defining the function is turned into
the attribute `Function = x*sin(x)`

. It is accessible
via a corresponding `slot`

of
the object:

f::Function

One can change the object by reassigning a new value to this attribute:

f::Function := 1/x: plot(f):

delete f:

For implicit plots as produced by `plot::Implicit2d`

and `plot::Implicit3d`

,
the attribute `Function`

refers to the function whose
zero set is to be plotted:

p := plot::Implicit2d(y*sin(x) - x*cos(y), x=-5..5, y=-5..5):

Internally, the expression defining the function is turned into
the attribute `Function = y*sin(x) - x*cos(y)`

. It
is accessible via a corresponding `slot`

of the object:

p::Function

delete p:

For parametrized curves and surfaces, the attributes `XFunction`

, `YFunction`

etc.
correspond to the parametrization of the coordinates *x*, *y* etc:

c2 := plot::Curve2d([u*cos(u), u*sin(u)], u = 0..5*PI): c2::XFunction, c2::YFunction

c3 := plot::Curve3d([u*cos(u), u*sin(u), u^2], u = 0..5*PI): c3::XFunction, c3::YFunction, c3::ZFunction

s := plot::Surface([u*cos(v), u*sin(v), u^2*sin(2*v)], u = 0..1, v = 0..2*PI): s::XFunction, s::YFunction, s::ZFunction

delete c2, c3, s:

Wherever a function expression is expected, also a `piecewise`

object or
a procedure can be used:

f1 := piecewise([x < 0, 0], [x >= 0, x]): f2 := proc(x) begin if x < 0 then 1 else 1 - x^2/2 end_if; end_proc: F1 := plot::Function2d(f1, x = -1..PI/2): F2 := plot::Function2d(f2, x = -1..PI/2): F1::Function, F2::Function

plot(F1, F2)

delete f1, f2, F1, F2:

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