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How does Excel 2003 calculate trendlines with respect to axes?
I'm using Excel 2003. Excel is giving me the wrong equation for the
trendline it produced. The curve resembles a parabola pointed downward with a positive offset on the yaxis. The xaxis has points 80, 70, 60, ..., 60, 70, 80. I changed the yaxis so that it crosses the xaxis at point zero. I do not believe that zero on my xaxis is zero according to the way it comes up with the trendline equation. I wish to figure out how to set up my xaxis with positive and negative numbers and still have the equation for the trendline be accurate. 
#2




Steve 
Make sure you're using an XY Scatter chart, and not a line chart. Make sure you are looking at the trendline formula with sufficient decimal places to assess the coefficients. If you're making a linear or poly fit, the sign of the data values will not affect the accuracy of the coefficients calculated.  Jon  Jon Peltier, Microsoft Excel MVP Peltier Technical Services Tutorials and Custom Solutions http://PeltierTech.com/ _______ BeefmanSteve wrote: I'm using Excel 2003. Excel is giving me the wrong equation for the trendline it produced. The curve resembles a parabola pointed downward with a positive offset on the yaxis. The xaxis has points 80, 70, 60, ..., 60, 70, 80. I changed the yaxis so that it crosses the xaxis at point zero. I do not believe that zero on my xaxis is zero according to the way it comes up with the trendline equation. I wish to figure out how to set up my xaxis with positive and negative numbers and still have the equation for the trendline be accurate. 
#3




Jon, I was using a line chart. I tried using the XY Scatter chart, and that
fixed the problem. Thanks one million! Steve "Jon Peltier" wrote: Steve  Make sure you're using an XY Scatter chart, and not a line chart. Make sure you are looking at the trendline formula with sufficient decimal places to assess the coefficients. If you're making a linear or poly fit, the sign of the data values will not affect the accuracy of the coefficients calculated.  Jon  Jon Peltier, Microsoft Excel MVP Peltier Technical Services Tutorials and Custom Solutions http://PeltierTech.com/ _______ BeefmanSteve wrote: I'm using Excel 2003. Excel is giving me the wrong equation for the trendline it produced. The curve resembles a parabola pointed downward with a positive offset on the yaxis. The xaxis has points 80, 70, 60, ..., 60, 70, 80. I changed the yaxis so that it crosses the xaxis at point zero. I do not believe that zero on my xaxis is zero according to the way it comes up with the trendline equation. I wish to figure out how to set up my xaxis with positive and negative numbers and still have the equation for the trendline be accurate. 
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