# 3.4 Java3003: drawing graphs with turtles and pixels  (Page 7/13)

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There is nothing new in Listing 8 . You should be able to correlate the code in Listing 8 and the drawing parameters in Listing 7 with the steps presented earlier to understand how the program named Parabola01 produces the output image shown in Figure 6 .

## A cubic

The program named Cubic01 shown in Listing 17 produces the graphic output shown in Figure 9

Figure 9. Graphic output from the program named Cubic01.

About the only thing that is different between the program named Parabola01 and the program named Cubic01 is the methodnamed function . In the program named Parabola01 , the method computes and returns the square of the incoming x-value. In theprogram named Cubic01 , the method computes and returns the cube of the incoming x-value. Just about everything that was said about Parabola01 also applies to Cubic01 .

## A circle

There are several ways to graph all of the functions discussed in this lesson. The previous sections have illustrated only one way -- using a turtle tograph the function. I will illustrate the following two ways to graph a circle in this section and will compare some of the advantages and disadvantages of each approach :

• Using a turtle to graph the function
• Accessing and setting pixel colors

## First approach

The first approach that I will present and explain uses a turtle to graph a circle. This program is very similar to the program named Parabola01 , but there are a few differences. I will explain those differences.

The program named Circle01 shown in Listing 18 produces the graphic output shown in Figure 10 .

Figure 10. Graphic output from the program named Circle01.

The first difference that is worthy of note is shown by the lines of code involving the variable named rVal in Listing 9 .

Listing 9 . The variable named rVal. ```double rVal = 0.6;//radius relative to 1.0 double yVal = 0;int row = 0; int col = 0;double xVal = -rVal; double xInc = 2*rVal/100;turtle.setPenColor(Color.BLUE);```

The variable named rVal is used to specify the radius of the circle relative to a value of 1.0 as declared and initialized in Listing 9 .

In the previous sections, we have evaluated our equation for a set of 101 x values ranging from -1.0 to +1.0. For the case of the circle, we will evaluatethe equation for a set of 101 x values ranging from -rVal to +rVal . ( There is no point in evaluating the equation outside of the circle.)

The code in Listing 9 declares and initializes the variable named rVal . Further down, the code sets the initial value for xVal to -rVal . Below that, the code sets the x-increment ( xInc ) to the diameter of the circle divided by 100. This will cause the equation for the circle to beevaluated at 101 points from left to right across the circle shown in Figure 10 .

## The method named function for Circle01

The method named function is shown in Listing 10 .

This method evaluates and returns the y-value for each incoming x-value for a circle with no offset, centered at the origin.The method evaluates the standard equation for a circle given by

`radius*radius = x*x + y*y`

Note that unlike the function method for Parabola01 and Cubic01 , this method requires two incoming parameters: the radius and the current x-value.

#### Questions & Answers

What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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