# 3.4 Java3003: drawing graphs with turtles and pixels  (Page 4/13)

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I will return to a discussion of the run method later.

The method named function is shown in its entirety in Listing 2 . This method evaluates and returns the y-value for each incoming x-valueto define a line described by the equation given above.

Listing 2 . The method named function for Line01. ```double function(double xVar,double slope,double yIntercept){ double yVar = (yIntercept) + (slope*xVar);return yVar; }//end function```

As you can see, this method is very simple. I decided to break it out as a separate method to clearly distinguish it from the other code in the run method. This will be the case in all of the programs that I explain in thislesson.

## Scaling

As I mentioned earlier, the more complex problem is to get everything scaled properly to produce a visually pleasing graph in the space provided by the World object as shown in Figure 3 .

Another issue that increases the complexity is the need sometimes to translate the origin from the default upper-left corner of the World object to a point at the center of the world.

And if that isn't enough, the problem is further complicated by the need to use mixed-mode arithmetic involving both int and double data types. Coordinate values in the world must be specified as type int . However, if an attempt is made to do all of the arithmetic using integerarithmetic, the results will often be incorrect with no warning. For example, with integer arithmetic, 1divided by 3 is equal to 0 instead of 0.3333. That fact alone can result in major errors.

The computations in this and the other programs in this lesson will take the following general form (although some of the steps may be combined in the actual code and may not be easy to isolate) .

Step 1 . Evaluate the y-value using the equation for a straight line at a set of 101 points along thex-axis ranging from -1.0 through +1.0. Use double-precision arithmetic and return the result as type double . This produces y values for the following set of x values:

`-1.0 -0.98 ... 0.0 ... 0.98 1.0`

Step 2 . Scale the x and y values by scale factors that produce a pleasing visual display in the available space of the world. For the BLUE line shown in Figure 3 with a slope of 1.0 and a y-intercept value of 0.0 in a 300x300 world, this producesthe following x (col) and y (row) values:

```-150,-150 -147,-147... 0,0... 147,147150,150```

Column numbers less than zero are off the left side of the world and row numbers less than 0 are off the top of the world. The origin of the world is atthe upper-left corner by default.

Step 3. Adjust the column number by adding one-half the width of the world and adjust the row number by adding one-half the height of the world, This translates theorigin to the center of the world. Use these values when telling the turtle to move to a particular location specified by a column number and a row number.

While this approach may seem overly complicated, it has one major advantage. In particular, the results are independent ofthe dimensions of the world. For example, the results shown in Figure 3 are for a 300x300 world. If I were to change the dimensions of the world to 400x150near the top of Listing 15 without making any other changes relative to Figure 3 , the output would change to that shown in Figure 5 , which is still correct.

#### Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
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?
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
what does nano mean?
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?
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
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?
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
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
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?
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 ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
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
how did you get the value of 2000N.What calculations are needed to arrive at it
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