AW: Questions on fitting and plotting data

*To*: mathgroup at smc.vnet.net*Subject*: [mg7969] AW: [mg7952] Questions on fitting and plotting data*From*: Buttgereit <Buttgereit at compuserve.com>*Date*: Wed, 30 Jul 1997 02:37:36 -0400*Sender*: owner-wri-mathgroup at wolfram.com

Hi Daniel, what you have seems to be a list of mean values (as you have SD or SEM). = If you want to fit a line to your data you should drop the errors before fitting: linefunc=3DFit[ Drop[#,-1]&/@yourData, {1,x}, x] will drop the last element in each row (that is: the error) returning the= equation of the line fit to your data. The information on the error of ea= ch point is not taken into account. You can see your fit result with the data using this: Plot[ linefunc, {x, 0,10}, Prolog->First[ plot1 ] ] First[ plot1 ] extracts the graphics primitives from the graphics object you have created with ErrorListPlot[ ... ]. Prolog will prepend these primitives to the list of primitives created by linefunc so they will be shown together in the graphics created by Plot[ ... ]. This should be what you intend at the moment... You can find information on this topic in the information package of the Statistics`LinearRegression` Package (provided you have Mathematica V. 3 = - for V. 2.2 I think you will need the "Guide to Standard Mathematica Packages" available by Wolfram Research). = If you want the available responses (which are averaged in your present data) to be taken into account, you will find a solution here, too: Regress[ ] is able to use multiple responses. Note that you have to read in the Package: = <<Statistics`LinearRegression` Good luck, Peter ---------- >Subject: [mg7969] [mg7952] Questions on fitting and plotting data I am *very* low on the Mma learning curve so this may be obvious, but here is what I am trying to do. I have a set of data that I want to plot, fit, and then plot the fit over it. The problem I am having is getting the correct fit and getting it to plot. Here is what I have so far... In[38]:=3D t2 =3D {{1, 1.5, .5}, {2.3, 2.8, .5}, {3, 3.7, .5}, {4.2, 4.6, .5}, {5.1, 5, .5}, {6.4, 6.4, .5}, {7.2, 7.7, .5}, {8, 8.9, .5}} Out[38]=3D {{1,1.5,0.5},{2.3,2.8,0.5},{3,3.7,0.5},{4.2,4.6,0.5},{5.1,5,0.5},{6.4,6.4= , 0.5},{7.2,7.7,0.5},{8,8.9,0.5}} In[39]:=3D plot1 =3D ErrorListPlot[t2] **now, here is where I start getting the problems - this is obviously NOT the correct least-square fit solution to the data I have specified.** In[40]:=3D fit1 =3D Fit[t2, {1, x }, {x, y}] Out[40] =3D 0.5-5.55112x10^-17 x In[41]:=3D Plot [fit1, {x, 0, 10}] In[37]:=3D Show [%, plot1] Any help will be greatly appreciated. Many thanks -daniel -------------------- daniel l. goscha dgoscha at phy.ilstu.edu <*>