Dear mailing list, I have following array:
X2 Y2 [1,] 422.7900 6.0 [2,] 469.8007 10.5 [3,] 483.9428 11.0 [4,] 532.4917 25.5 [5,] 596.1942 33.5 [6,] 630.8496 40.5 [7,] 733.2996 45.0 [8,] 946.4779 32.0 [9,] 996.8068 35.5 [10,] 1074.3310 23.0 I do afterwards the following: plot.new() plot.window(xlim=c(min(X1)-50,max(X1)+50), ylim=c(min(Y1)-25,max(Y1)+25)) axis(2, cex.axis=1.2) axis(1, cex.axis=1.2) points(X2, Y2, type="p", pch=0, cex=1.2, col="black") title(main="Dyke Geometry Along Strike", cex.main=1.2, font.main=4) title(xlab="distance [m]", cex.lab=1.2) title(ylab="half-thickness [m]", cex.lab=1.2) box() I would like curve fitting where I proceeded with a non linear-regression with the according function below: nls(formula = Y2 ~ abs(b*abs(1-X2^2/a^2)^(1/2)), start = list( a=282, b=40)) The formula should give the y-positive part of an ellipse in my opinion or I might be completely wrong. In the end I would like to fit a curve of half an ellipse through the data. I might could do this as well with a 2nd order polynomial fit. I am grateful for any suggestions and comments to my problem. Cheers -- Niklaus Hürlimann Doctorant-PhD Université de Lausanne Institut de Minéralogie et Géochimie L'Anthropole CH-1015 Lausanne Suisse E-mail: niklaus.hurlim...@unil.ch Tel:+41(0)21 692 4452 [[alternative HTML version deleted]]
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