Simple Problem: Plotting mathematical functions

[Aye]

Never mind, thanks for your help, I got it. Yay

Hey there,
I want to plot 5 parabola functions, which happen to be
f(x) = 0.25x² + 6,47x -32.6
g(x)=0.99x² -6x -195
j(x)= 0.77x² +14x -495
k(x)=0.001x² + 65x -785
l(x) = 0.9x² -2x -636

in the same graph. Sadly I even do not really understand how to plot just one graph...
I found this code in the Internet, which plots a cos-function:

>x <- seq( -10, 10, length = 1000)
>plot(x, sin(x), xlab="x-values", ylab="f(x)", type="l")
>lines(x, cos(x), lty=3)
>title( "Trigonometric functions", "sin(x) and cos(x)")

If I replace the sin(x) thing (bold) with one of my functions, it doesn't work and reports an unwanted character.

Can somebody help me with that?

[Yellow]

Hi,

At the moment I am studying R at school.
But I found this site very useful to explain the plot functions to me:

http://www.harding.edu/fmccown/r/ 

Maybe that can help you too?

[Aye]

Okay, i got this far:
f <- function(x) 0.25*x^2 + 6.47*x -32.6
g <- function(x) 0.99*x^2 -6*x -195
h <- function(x) 0.77*x^2 +14*x -495
j <- function(x) 0.001*x^2 + 65*x -785
k <- function(x) 0.9*x^2 -2*x -636
plot(x, f(x), xlab="Elemente in der Reihung", ylab="Indexwert des
Sortieraufwands"), type="l")
// lines(x, g(x), lty=3) //Not sure if it works, but this is irrelevant atm.

As soon as R does the plot command, he states that x is an object he can't
find.
So i propably have to do something like x <- XXXXXXXXXX. What do I insert
for the XXXXXXXXX to make it have the values - say - from 15 to 10000?

Thanks again.

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[Michael Weylandt]

It seems that your first problem is syntax:

2x

will thrown an error, while

2*x

won't.

Google around for a good intro tutorial (there's the main one you can
access by typing help.start() and it's quite good) and these sorts of
things will be explained.

You might also want to use the curve function (type ?curve at the
prompt for details)

e.g.,

curve(x^2, from = 0, to = 5)

plots x^2 from x = 0 to x = 5 and handles axes nicely.

Michael

On Thu, Apr 12, 2012 at 2:29 PM, Aye <[hidden email]> wrote:

> Hey there,
> I want to plot 5 parabola functions, which happen to be
> f(x) = 0.25x² + 6,47x -32.6
> g(x)=0.99x² -6x -195
> j(x)= 0.77x² +14x -495
> k(x)=0.001x² + 65x -785
> l(x) = 0.9x² -2x -636
>
> in the same graph. Sadly I even do not really understand how to plot just
> one graph...
> I found this code in the Internet, which plots a cos-function:
>
>>x <- seq( -10, 10, length = 1000)
>>plot(x, *sin(x)*, xlab="x-values", ylab="f(x)", type="l")
>>lines(x, cos(x), lty=3)
>>title( "Trigonometric functions", "sin(x) and cos(x)")
>
> If I replace the sin(x) thing (bold) with one of my functions, it doesn't
> work and reports an unwanted character.
>
> Can somebody help me with that?
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Simple-Problem-Plotting-mathematical-functions-tp4552668p4552668.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

[Matthieu Dubois-3]

Hi,

you can use the curve() function for this. It is dedicated to plotting
functions.

Here is an example

# turn your functions into r functions
f <- function(x) 0.25 * x^2 + 6.47 * x -32.6
g <- function(x) 0.99*x^2 -6*x -195
j <- function(x) 0.77*x^2 + 14*x -495
k <- function(x) 0.001*x^2 + 65*x -785
l <- function(x) 0.9*x^2 -2*x -636

# plot f and g
curve(f, from=0, to=100, lty=1)
curve(g, add=TRUE, lty=2)


In this example, the parameters 'from' and 'to' define the domain over wich
all functions will be evaluated. The parameter add=TRUE is used to add
the second function to the previous plot.

HTH

Matthieu

Matthieu Dubois
Post-doctoral fellow,
Psychology Department, Univeristé Libre de Bruxelles

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[David Winsemius]

On Apr 12, 2012, at 3:49 PM, Aye wrote:

> Okay, i got this far:
> f <- function(x) 0.25*x^2 + 6.47*x -32.6
> g <- function(x) 0.99*x^2 -6*x -195
> h <- function(x) 0.77*x^2 +14*x -495
> j <- function(x) 0.001*x^2 + 65*x -785
> k <- function(x) 0.9*x^2 -2*x -636
> plot(x, f(x), xlab="Elemente in der Reihung", ylab="Indexwert des
> Sortieraufwands"), type="l")
> // lines(x, g(x), lty=3) //Not sure if it works, but this is  
> irrelevant atm.
>
> As soon as R does the plot command, he states that x is an object he  
> can't
> find.
> So i propably have to do something like x <- XXXXXXXXXX. What do I  
> insert
> for the XXXXXXXXX to make it have the values - say - from 15 to 10000?

x <- seq(15, 1000, by=5)

>
> Thanks again.
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Simple-Problem-Plotting-mathematical-functions-tp4552668p4552894.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
West Hartford, CT

______________________________________________
[hidden email] mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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[Rick Bilonick-2]

On 04/12/2012 09:11 PM, David Winsemius wrote:

>
> On Apr 12, 2012, at 3:49 PM, Aye wrote:
>
>> Okay, i got this far:
>> f <- function(x) 0.25*x^2 + 6.47*x -32.6
>> g <- function(x) 0.99*x^2 -6*x -195
>> h <- function(x) 0.77*x^2 +14*x -495
>> j <- function(x) 0.001*x^2 + 65*x -785
>> k <- function(x) 0.9*x^2 -2*x -636
>> plot(x, f(x), xlab="Elemente in der Reihung", ylab="Indexwert des
>> Sortieraufwands"), type="l")
>> // lines(x, g(x), lty=3) //Not sure if it works, but this is
>> irrelevant atm.
>>
>> As soon as R does the plot command, he states that x is an object he
>> can't
>> find.
>> So i propably have to do something like x <- XXXXXXXXXX. What do I
>> insert
>> for the XXXXXXXXX to make it have the values - say - from 15 to 10000?
>
> x <- seq(15, 1000, by=5)
>
>
>>
>> Thanks again.
>>
>> --
>> View this message in context:
>> http://r.789695.n4.nabble.com/Simple-Problem-Plotting-mathematical-functions-tp4552668p4552894.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
>> ______________________________________________
>> [hidden email] mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> David Winsemius, MD
> West Hartford, CT
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

You can certainly use "plot" but you could also use "curve":

 > curve(0.25*x^2 + 6.47*x -32.6,0,10)
 > f <- function(x) 0.25*x^2 + 6.47*x -32.6
 > curve(f)
 > curve(f,0,100)

Rick

--
---
Richard A. Bilonick, PhD
Assistant Professor
412 647 5756
Dept. of Ophthalmology, School of Medicine
Dept. of Biostatistics, Graduate School of Public Health
Principal Investigator: Pittsburgh Aerosol Research and Inhalation Epidemiology Study (PARIES)
University of Pittsburgh

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