topic Re: Error fitting of a slope in mathcad in Mathcad https://www.ptcusercommunity.com/t5/Mathcad/Error-fitting-of-a-slope-in-mathcad/m-p/334918#M130979 <HTML><HEAD></HEAD><BODY><P>Use stderr(P,P.n)=</P><P>Via help you can access a helpul quicksheet about Linear Regression.</P></BODY></HTML> Sun, 27 Oct 2013 17:55:12 GMT Werner_E 2013-10-27T17:55:12Z Error fitting of a slope in mathcad https://www.ptcusercommunity.com/t5/Mathcad/Error-fitting-of-a-slope-in-mathcad/m-p/334917#M130978 Hello,I have a submission tomorrow and I need to calculate the error in my calculated value of the intercept c and gradient m.I have used both the mathcad function and the manual version of it to fit my data points to a line (finding alpha and beta for a langmuir isotherm) and now Thu, 03 May 2018 16:47:57 GMT https://www.ptcusercommunity.com/t5/Mathcad/Error-fitting-of-a-slope-in-mathcad/m-p/334917#M130978 FrankButcher 2018-05-03T16:47:57Z Re: Error fitting of a slope in mathcad https://www.ptcusercommunity.com/t5/Mathcad/Error-fitting-of-a-slope-in-mathcad/m-p/334918#M130979 <HTML><HEAD></HEAD><BODY><P>Use stderr(P,P.n)=</P><P>Via help you can access a helpul quicksheet about Linear Regression.</P></BODY></HTML> Sun, 27 Oct 2013 17:55:12 GMT https://www.ptcusercommunity.com/t5/Mathcad/Error-fitting-of-a-slope-in-mathcad/m-p/334918#M130979 Werner_E 2013-10-27T17:55:12Z Re: Error fitting of a slope in mathcad https://www.ptcusercommunity.com/t5/Mathcad/Error-fitting-of-a-slope-in-mathcad/m-p/334919#M130980 <HTML><HEAD></HEAD><BODY><P>Thanks for the quick response Werner,</P><P></P><P>I have already tried this however I want to know the error attributed to the propagation of the uncertainties in my values of eta.</P><P></P><P>Do you have any idea how to do this mathetmatically?</P><P></P><P>Also I have calculated errors for another part of the paper, however they are errors in a value of x. I have plotted x against a varying y and don't seem to be able to add error bars that represent the errors in the value of x; how would I go about doing this? See attached.</P><P></P><P>Cheers</P><P>Fraser</P></BODY></HTML> Sun, 27 Oct 2013 18:07:47 GMT https://www.ptcusercommunity.com/t5/Mathcad/Error-fitting-of-a-slope-in-mathcad/m-p/334919#M130980 FrankButcher 2013-10-27T18:07:47Z Re: Error fitting of a slope in mathcad https://www.ptcusercommunity.com/t5/Mathcad/Error-fitting-of-a-slope-in-mathcad/m-p/334920#M130981 <HTML><HEAD></HEAD><BODY><BLOCKQUOTE><TABLE border="1"><TBODY><TR><TD><P>I have already tried this however I want to know the error attributed to the propagation of the uncertainties in my values of eta.</P></TD></TR></TBODY></TABLE></BLOCKQUOTE><P>I am not sure what exactly this error should measure and how you would define it.</P></BODY></HTML> Sun, 27 Oct 2013 18:39:34 GMT https://www.ptcusercommunity.com/t5/Mathcad/Error-fitting-of-a-slope-in-mathcad/m-p/334920#M130981 Werner_E 2013-10-27T18:39:34Z Re: Error fitting of a slope in mathcad https://www.ptcusercommunity.com/t5/Mathcad/Error-fitting-of-a-slope-in-mathcad/m-p/334921#M130982 <HTML><HEAD></HEAD><BODY><P>The values used to calculate the intercept and slope of the line are gathered from a simulation and as such each data point has an individual uncertainty attributed to it. I would like to correlate these uncertainties to get the maximum error in the calculated values of y-intercept and gradient.</P><P></P><P>Is this possible analytically?</P></BODY></HTML> Sun, 27 Oct 2013 18:46:40 GMT https://www.ptcusercommunity.com/t5/Mathcad/Error-fitting-of-a-slope-in-mathcad/m-p/334921#M130982 FrankButcher 2013-10-27T18:46:40Z Re: Error fitting of a slope in mathcad https://www.ptcusercommunity.com/t5/Mathcad/Error-fitting-of-a-slope-in-mathcad/m-p/334922#M130983 <HTML><HEAD></HEAD><BODY><P>As I understand you just want to know how you values of eta influence the aberration of (P; Pn) from a perfect straight line!?</P><P>You get a straight line if you vector eta consists of numers all equal.</P><P>You you have to set up a measure for the aberration of a vector from a constant vector.</P><P>Maybe something like this???</P><P><IMG __jive_id="60267" class="jive-image" alt="eta1.png" src="https://community.ptc.com/legacyfs/online/60267_eta1.png" /></P></BODY></HTML> Sun, 27 Oct 2013 18:53:47 GMT https://www.ptcusercommunity.com/t5/Mathcad/Error-fitting-of-a-slope-in-mathcad/m-p/334922#M130983 Werner_E 2013-10-27T18:53:47Z