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re: Excel help
Posted on 9/15/15 at 1:40 pm to Sigma
Posted on 9/15/15 at 1:40 pm to Sigma
I think I might see what's happening. A four-order poly gives the following (and the line is perfectly through the points):
y = 15297x4 - 457991x3 + 5E+06x2 - 3E+07x + 5E+07
R² = 0.9999
The x4, x3, etc. are actually x^4, x^3, etc.
Yet.....I plugged in 6.27 and get some nonsensical answer- negative 30.8 million. I think the XLS reported coefficients are not providing enough significant digits and that is what's messed up. Note the 5.00 million, 30.0 million and 50.0 million coefficients. The rounded (truncated) diffs is what's busting the equation. Would need to do the calcs manually (or program) to get the precise coefficients. An XLS bug, it appears. Somebody shout if that's not it.
y = 15297x4 - 457991x3 + 5E+06x2 - 3E+07x + 5E+07
R² = 0.9999
The x4, x3, etc. are actually x^4, x^3, etc.
Yet.....I plugged in 6.27 and get some nonsensical answer- negative 30.8 million. I think the XLS reported coefficients are not providing enough significant digits and that is what's messed up. Note the 5.00 million, 30.0 million and 50.0 million coefficients. The rounded (truncated) diffs is what's busting the equation. Would need to do the calcs manually (or program) to get the precise coefficients. An XLS bug, it appears. Somebody shout if that's not it.
1
Posted on 9/15/15 at 1:43 pm to K E V 8 4
Solution: divide all of your Y data points by 10,000. Regress. Then take result of equation and multiply by 10,000. The equation and RSq are as follows:
y = 1.5297x4 - 45.799x3 + 515.07x2 - 2580.4x + 4862.3
R² = 0.9999
Answer: 71,386
y = 1.5297x4 - 45.799x3 + 515.07x2 - 2580.4x + 4862.3
R² = 0.9999
Answer: 71,386
This post was edited on 9/15/15 at 1:51 pm
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