Turtle Graphics in R

Description

Learn computer programming while having a jolly time

Details

Move the Turtle with commands that are relative to its own position, e.g., "move forward 100 pixels" or "turn right 30 degrees". From these building blocks you can build more complex shapes like circles, fractals, etc. Combined with R control flow, functions, and recursion, the idea of Turtle graphics allows students to get familiar with computer programming in a very accessible and pleasant way.

Author(s)

Anna Cena [aut]
Marek Gagolewski [aut]
Marcin Kosinski [aut]
Natalia Potocka [aut] Barbara Zogala-Siudem [aut, cre]

See Also

Other TurtleGraphics: turtle_do, turtle_getpos, turtle_goto, turtle_init, turtle_move, turtle_param, turtle_reset, turtle_show, turtle_status, turtle_turn, turtle_up

Evaluate a Larger Portion of Turtle Drawing Code

Description

turtle_do evaluates an R expression with the Turtle temporarily hidden (for performance reasons).

Usage

turtle_do(expr)

Arguments

Details

The terrarium must be initialized prior to using these functions, see turtle_init.

In order to decrease the evaluation time of expr, it is evaluated with Turtle temporarily hidden. Basically it means that if a Turtle image is visible (see turtle_show and turtle_hide) turtle_do removes it, evaluates expr and redraws it on the function exit.

See Also

Other TurtleGraphics: TurtleGraphics-package, turtle_getpos, turtle_goto, turtle_init, turtle_move, turtle_param, turtle_reset, turtle_show, turtle_status, turtle_turn, turtle_up

Examples

turtle_init()
turtle_do({
   for (i in 1:4) {
      turtle_forward(50)
      turtle_right(90)
   }
})

Get the Turtle's Current Position and Direction

Description

turtle_getpos returns the Turtle's current position on the plane.

turtle_getangle returns the Turtle's current direction, in degrees. An angle of 0 represents a north-facing Turtle.

Usage

turtle_getpos()

turtle_getangle()

Details

The terrarium must be initialized prior to using these functions, see turtle_init.

Value

Both functions return a (named) numeric vector. turtle_getpos returns a vector of length two which specifies the x and y coordinates. The turtle_getangle returns the angle.

See Also

Other TurtleGraphics: TurtleGraphics-package, turtle_do, turtle_goto, turtle_init, turtle_move, turtle_param, turtle_reset, turtle_show, turtle_status, turtle_turn, turtle_up

Examples

turtle_init()
turtle_getpos()["x"] # x coordinate
turtle_getpos()["y"] # y coordinate

Set the Turtle's Position and Direction

Description

turtle_goto and turtle_setpos move the Turtle to a given location without changing its direction.

turtle_setangle rotates the Turtle to a given (absolute) angle, where 0 denotes a north-facing Turtle.

Usage

turtle_goto(x, y)

turtle_setpos(x, y)

turtle_setangle(angle)

Arguments

Details

The terrarium must be initialized prior to using these functions, see turtle_init.

If the given location (x, y) lies outside the terrarium, the behavior of these functions depends on the mode argument in turtle_init.

turtle_goto may draw the path between the current Turtle's position and the new location. Its behavior depends on the current plot settings, see turtle_up, turtle_down. In case of turtle_setpos, however, the path drawing is always disabled.

See Also

Other TurtleGraphics: TurtleGraphics-package, turtle_do, turtle_getpos, turtle_init, turtle_move, turtle_param, turtle_reset, turtle_show, turtle_status, turtle_turn, turtle_up

Set Up a New, Shiny Terrarium

Description

This function creates a new empty plot with the Turtle centered on the board and facing to the north.

Usage

turtle_init(width = 100, height = 100, mode = c("error", "clip", "cycle"))

Arguments

Details

The mode argument determines what happens if the Turtle tries to move outside the terrarium. clip allows it to do that, but the drawing will be clipped to the predefined plot region. error throws an error. cycle makes the Turtle appear on the other side of the board.

After the turtle_init() function has been called you can e.g. move the Turtle with the turtle_forward function, turn its direction with turtle_right or set display parameters of the Turtle's trace, see turtle_param.

See Also

Other TurtleGraphics: TurtleGraphics-package, turtle_do, turtle_getpos, turtle_goto, turtle_move, turtle_param, turtle_reset, turtle_show, turtle_status, turtle_turn, turtle_up

Move the Turtle Forward or Backward

Description

turtle_forward moves the Turtle in forward direction and turtle_backward moves the Turtle back.

Usage

turtle_move(distance, direction = c("forward", "backward"))

turtle_forward(distance)

turtle_backward(distance)

Arguments

Details

The Turtle must be initialized prior to using these functions, see turtle_init.

These functions make use of the Turtle's display options specified by the turtle_param function (or if not, use the default options set by turtle_init).

Note that if turtle_up or turtle_down was called, the Turtle's trace will be or not be drawn, respectively.

If you are willing to call these functions in an R loop, you may want to hide the Turtle temporarily (see turtle_hide and turtle_do) before making actual moves. This will increase the drawing performance significantly.

See Also

Other TurtleGraphics: TurtleGraphics-package, turtle_do, turtle_getpos, turtle_goto, turtle_init, turtle_param, turtle_reset, turtle_show, turtle_status, turtle_turn, turtle_up

Examples

turtle_init()
turtle_left(30)
turtle_forward(2)
turtle_up()
turtle_forward(1)
turtle_down()
turtle_right(60)
turtle_forward(9)

Set Display Options

Description

Sets the display options for the Turtle's trace. It is possible to change its color, line type and line width.

Usage

turtle_param(col = NULL, lwd = NULL, lty = NULL)

turtle_col(col)

turtle_lwd(lwd)

turtle_lty(lty)

Arguments

Details

The Turtle must be initialized prior to using this function, see turtle_init.

See Also

Other TurtleGraphics: TurtleGraphics-package, turtle_do, turtle_getpos, turtle_goto, turtle_init, turtle_move, turtle_reset, turtle_show, turtle_status, turtle_turn, turtle_up

Examples

turtle_init()
turtle_forward(5)
turtle_up()
turtle_forward(3)
turtle_down()
turtle_left(90)
turtle_forward(5)
turtle_param(col = "red", lwd = 2, lty = 2)
turtle_forward(5)

Reset the Turtle's Position and Direction

Description

This function resets the Turtle's position, direction, and graphical options.

Usage

turtle_reset()

Details

The Turtle must be initialized prior to using this function, see turtle_init.

After a call to this function, the Turtle will be placed in the terrarium's center and it will be directed to the north.

The drawing remains unchanged.

See Also

Other TurtleGraphics: TurtleGraphics-package, turtle_do, turtle_getpos, turtle_goto, turtle_init, turtle_move, turtle_param, turtle_show, turtle_status, turtle_turn, turtle_up

Examples

turtle_init()
turtle_forward(4)
turtle_param(col="red", lty=2, lwd=3)
turtle_reset()
turtle_left(45)
turtle_forward(3)

Show or Hide the Turtle

Description

These functions enable or disable displaying the Turtle's image on the screen.

Usage

turtle_show()

turtle_hide()

Details

The Turtle must be initialized prior to using this function, see turtle_init.

It is recommended to hide the Turtle when performing multiple Turtle moves, for efficiency reasons, see also turtle_do.

See Also

Other TurtleGraphics: TurtleGraphics-package, turtle_do, turtle_getpos, turtle_goto, turtle_init, turtle_move, turtle_param, turtle_reset, turtle_status, turtle_turn, turtle_up

Examples

turtle_init()
turtle_forward(4)
turtle_hide()
turtle_left(30)
turtle_forward(3)

Read the Turtle's Status

Description

This function gives information about the current Turtle's position, direction, and on display options.

Usage

turtle_status()

Details

The Turtle must be initialized prior to using this function, see turtle_init.

Value

Returns a list with three elements.

See Also

Other TurtleGraphics: TurtleGraphics-package, turtle_do, turtle_getpos, turtle_goto, turtle_init, turtle_move, turtle_param, turtle_reset, turtle_show, turtle_turn, turtle_up

Turn (Rotate) the Turtle

Description

Turn the Turtle in the given direction by the given angle.

Usage

turtle_turn(angle, direction = c("left", "right"))

turtle_left(angle)

turtle_right(angle)

Arguments

Details

The Turtle must be initialized prior to using this function, see turtle_init.

See Also

Other TurtleGraphics: TurtleGraphics-package, turtle_do, turtle_getpos, turtle_goto, turtle_init, turtle_move, turtle_param, turtle_reset, turtle_show, turtle_status, turtle_up

Examples

turtle_init()
turtle_left(30) # equivalent to turtle_turn(30, "left")
turtle_right(40)
turtle_turn(30, sample(c("left", "right"), 1)) # random turn

Turn on or off Turtle Trace Drawing

Description

When the Turtle moves, it may or may not leave a visible trace. These functions control such a behavior.

Usage

turtle_up()

turtle_down()

Details

The Turtle must be initialized prior to using this function, see turtle_init.

See Also

Other TurtleGraphics: TurtleGraphics-package, turtle_do, turtle_getpos, turtle_goto, turtle_init, turtle_move, turtle_param, turtle_reset, turtle_show, turtle_status, turtle_turn