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Topic: Evaluation Error message
Replies: 2   Last Post: Jun 7, 2008 2:05 AM

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Tim Erickson

Posts: 326
Registered: 12/6/04
Re: [Fathom & TP] Evaluation Error message
Posted: Jun 7, 2008 2:05 AM
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On Jun 6, 2008, at 11:43 AM, wrote:

> I am attempting to write a demonstration of power transformations to
> achieve linearity. I have created a data set with x defined as
> random integers from -5 to 5. The equation for y is (a(x-c)^p+d)^t
> with all variables controlled by sliders. Whenever x is a negative
> number I get an evaluation error for y. Understand that when p is a
> fraction with an even denominator and x-c is negative there is no
> solution but when I set p and t to integer values the left side of
> the parabola does not appear. I'm sure I'm doing something stupid
> but I just cannot see it. Can anyone help.

When I tried it, at first I had the same experience. But then I
noticed I had set p to 2 and t was still at its default 5. This was
not the problem! The problem was that d was so large that the function
was outside the window. (I have made this mistake countless times, so
I hope it's the one you made too!)

So set a = 1, c = 0, d = 0, and see if you can see the function.

With high hopes,

Tim Erickson * Epistemological Engineering
5269 Miles Avenue, Oakland CA 94618 * 510.653.3377

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