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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 CRigby[/i] [br]Origin Ver. and Service Release: OriginPro 2015 Sr2 b9.2.272 Operating System: Windows 10 Good day. I have a data set (given below) which is to be used to calibrate the readout of a wavelength tunable laser, which should be pretty linear. When applying a linear fit, the residuals appear to form a gaussian or bell shape. I would like to be able to account for this in my fit and thereby reduce the standard deviation as I believe this may be a real artefact of my system. In short I would like to know how one could fit a gaussian with a slanted base. I have tried the custom equation fitting by simply adding the equations for a line and an amplitude gaussian together, but I cannot get a fit with reasonable parameters. I have tried for more than a week now with various combinations, but now need to get this done soon. Either I have been doing something inherently wrong in the dialogs of the nonlinear fit option or I am on the wrong path entirely. If a kind soul could please help me with the correct equation and parameter values I would be greatful. X, Y, 22690.1928267043, 69086.24, 22684.785670402, 69080.8, 22684.0740016195, 69080.1, 22680.8964796708, 69076.91, 22678.6666749217, 69074.71, 22676.2146531386, 69072.25, 22672.4923786984, 69068.53, 22671.7455004067, 69067.8, 22670.757619993, 69066.81, 22665.5056185862, 69061.58, 22656.7802748621, 69052.92, 22648.1401256736, 69044.32, 22641.1386319183, 69037.29, 22639.9114833797, 69036.07, 22638.7838439886, 69034.92, 22631.8639897396, 69027.97, 22629.9172801845, 69026.02, 22628.6746546371, 69024.77, 22621.7996148322, 69017.87, 22619.1168497017, 69015.19, 22617.7114023542, 69013.78, 22610.9292187472, 69006.99, 22595.1570466788, 68991.2, 22586.8336476946, 68982.9, 22691.750493756, 69087.79, 22687.888409276, 69083.91, 22568.1702048066, 68964.12, 22559.811248376, 68955.7, 22573.6971957486, 68969.67, 22581.9899552147, 68978.04, [/quote]   Check here to include your profile signature. Check here to subscribe to this topic.