simultaneous fitting of two plots with two functions

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Arun Kumar Bar
Arun Kumar Bar 2018-9-16
评论： Arun Kumar Bar 2018-9-25
I have two sets of dependent variable column vectors (y1, y2) for a set of independent variable column vectors (x). I want to fit the (x, y1) plot with the function f1(ca. f1 = (a + (b-a)*(1 + c*x^d))) and the (x, y2) plot with the function f2(ca. f2 = (b-a)*c*x^d)) simultaneously. Could anyone please help?
Many thanks, in advance! Arun
  2 个评论
Kaushik Lakshminarasimhan
Kaushik Lakshminarasimhan 2018-9-16
What do you mean by simultaneous? Based on your equations, the transformation from x to y_1 is independent of y_2 and likewise x -> y_2 is independent of y_1. So you can just fit the two functions separately.
Arun Kumar Bar
Arun Kumar Bar 2018-9-17
编辑：Arun Kumar Bar 2018-9-17
The parameters a, b, c and d are to be same for both the fits. If I fit separately, it will not guarantee same values of the parameters for both the fits. Anyway, thank you.

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采纳的回答

Torsten
Torsten 2018-9-17
Use "lsqcurvefit" with the data set xdata = (x,x),ydata = (y1,y2).
Best wishes
Torsten.
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Torsten
Torsten 2018-9-25
... .*pi/2)))./(1+(2.* ...
instead of
... .*pi/2)))/(1+(2.* ...
Best wishes
Torsten.

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更多回答（1 个）

Torsten
Torsten 2018-9-17
xdata=[x(:,1); x(:,1)];
ydata=[y1(:,1); y2(:,1)];
fun=@(x,xdata) [f1(xdata(1:numel(xdata)/2),x(1),x(2),x(3),x(4)); f2(xdata(1:numel(xdata)/2),x(1),x(2),x(3),x(4))];
x0=[- - - -];
x=lsqcurvefit(fun,x0,xdata,ydata);
where f1(...),f2(...) must be column vectors each of the same size as x.

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