Re: [Phys-l] Grapher on macintosh

[ludwik kowalski <kowalskil@mail.montclair.edu>]

On Feb 22, 2008, at 3:26 PM, Steve Highland wrote:

> I spent some hours one day trying to get Grapher to work for me last  
> year.
> It was painful. Perhaps I can dig up some knowledge for you (but  
> don't hold
> your breath).
>
> One very disturbing thing about Grapher is that I've found it does not
> accurately plot functions relative to the grid marks!  I tried to  
> plot a
> piecewise continuous function and the pieces did not match up!
>
> Even worse, just try to plot this:
>
> Y = -(9/98)(x^2 -28x)
>
> This came out of a football kick problem I was trying to help out  
> with on
> Yahoo Answers.  It should have a maximum of y = 18 at x = 14 and it  
> should
> cross the x-axis at x=28.
>
> Whoa -- I was about to complain that the plot doesn't hit the grid  
> marks,
> but now I (finally!) see that there are SIX subdivisions for every  
> FIVE
> units on my plot.  Egad!  How in the world does something like that  
> come up
> automatically?  I suffered greatly a few months ago over this but  
> didn't see
> it till now.  Yikes.

I do not know why my file, attached to two messages, was not part of  
what I received. Is this because this file was extracted from Grapher  
or is it because I am having a problem with sending attachments. As a  
test let me attach a file that has nothing to do with Grapher. See  
below. I was showing that the curve plotted by Grapher was in very  
good agreement with the function posted by Steven. I suspect there was  
a typing error in his right side expression. The only place the x axis  
is intercepted is at the origin.  The values of y increase  
monotonically for all values of x.

The attached rtf file should appear below this line





Ludwik Kowalski, a retired physisist
5 Horizon Road, apt.2702, Fort Lee, NJ, 07024, USA
Also an amateur journalist at http://csam.montclair.edu/~kowalski/cf/