Polinomial - What's Wrong

  • Thread starter Thread starter Hugh
  • Start date Start date
H

Hugh

Hi All,
Please refer to the earlier Post. But here it is again.
Below is the data for a graph. x is the x axis, and Data the applicable Data
for the graph.
X Data formula
1.0000 0.0688 -0.0012
2.0000 0.1277 0.0370
3.0000 0.1800 0.0756
4.0000 0.2272 0.1146
5.0000 0.4471 0.1541
6.0000 0.6924 0.1940
7.0000 1.0000 0.2343
8.0000 1.3455 0.2751
9.0000 1.5503 0.3163
10.0000 1.7955 0.3580
11.0000 2.0820 0.4001

A Polinomial trendline is then applied to the graph line.
A polinmial graph has r2=.9894, so pretty good fit.
The trend formula is y = 0.0148x2 + 0.0375x - 0.0398
This is entered into the Formula column as
((0.0148*x)^2)+(0.0375*x)-0.0398

If this data is taken and put into the same graph as a new line it bears no
remblance to the original polinomial trend line.
Which part of how thick I am, is failing to grasp the simple answer to this?
Please be polite in replies, (though I may be too thick to understand them)
:)

Thanks
 
Please see the response(s) to your other post.

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Regards,

Tushar Mehta
www.tushar-mehta.com
Excel, PowerPoint, and VBA add-ins, tutorials
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Hi All,
Please refer to the earlier Post. But here it is again.
Below is the data for a graph. x is the x axis, and Data the applicable Data
Click to expand...
{snip}
 
Hi Hugh,

I can't work out what it is you have done wrong.
If your first X value is in A1 then the formula should be,

A1: =((0.0148*(A1*A1))+(0.0375*A1)-0.0398)

which returns 0.0125

This formula the dragged down produces a plot that is very close to the
trend line.

Cheers
Andy
 
Many thanks, I appreciate the help.

Hugh
Andy Pope said:
Hi Hugh,

I can't work out what it is you have done wrong.
If your first X value is in A1 then the formula should be,

A1: =((0.0148*(A1*A1))+(0.0375*A1)-0.0398)

which returns 0.0125

This formula the dragged down produces a plot that is very close to the
trend line.

Cheers
Andy
Click to expand...
 
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