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Screensize: 640 x 480 800 x 600 1024 x 768 1280 x 1024 UserName: Password: Anti-Spam Code: Format Mode: Basic  Help  Prompt  Format: Font Andale Mono Arial Arial Black Book Antiqua Century Gothic Comic Sans MS Courier New Georgia Impact Lucida Console Script MT Bold Stencil Tahoma Times New Roman Trebuchet MS Verdana   Size 1 2 3 4 5 6   Color Black Red Yellow Pink Green Orange Purple Blue Beige Brown Teal Navy Maroon LimeGreen Message: * HTML is OFF * Forum Code is ON Smilies [quote][i]Originally posted by bur2000[/i] [br]Origin Ver. and Service Release (Select Help-->About Origin): 8.6 Operating System: Win 7 I did a 9th order polynomial fit and Origin did output the fitting parameters B1-B9. The fit worked well, the values calculated by Origin are very close to the original values. However, when I use the parameters in Excel the calculated values differ significantly from those in Origin. It's not a problem in Excel, I used a pocket calculator and got the same wrong results. Here's the parameter table from Origin: Intercept 17.54397 B1 1.23021 B2 0.05444 B3 -0.01853 B4 0.00163 B5 -7.70248E-5 B6 2.15435E-6 B7 -3.58271E-8 B8 3.27741E-10 B9 -1.27133E-12 For x = 10.04374 Origin gets 27.2526715364701, but I get 27.20678141 (using Intercept + B1*x^1 + B2*x^2 and so on). I guess the Bx values in the report table are not the values actually used by Origin, but rounded ones. Is that so and how can I access the exact values Origin used? I need these for some calculation in Excel. Thanks. [/quote]   Check here to include your profile signature. Check here to subscribe to this topic.