Help Fit line / curve to data

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RuiQi
RuiQi 2016-11-23
评论： Walter Roberson 2016-11-23
Hello, I am trying to find the equation of a best fit line for this data that I have below. I tried using polynomial fit with degree 2 but the results are unsatisfactory. I was wondering if anyone can offer any suggestions. Based on the scatter plot below, id like the results to be a curve that is steep at a steep slope at the beginning and gentle later.
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RuiQi
RuiQi 2016-11-23
Hi thanks ! But id like to extract the complete equation of the curve as well.
KSSV
KSSV 2016-11-23
编辑：KSSV 2016-11-23
h = isline ;
h will be having the xdata and ydata.It fit's a straight line.

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回答（2 个）

Walter Roberson
Walter Roberson 2016-11-23
I suggest trying to fit it to y = A * exp(-B*x) + C
If you assume that C is 0 then that would be a fit of y = A * exp(-B*x) which would be
log(y) = log(A) - B * x
which would be a linear fit to find B and log(A).
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RuiQi
RuiQi 2016-11-23
Cool ! I would need to exponentiate log(A) so that I can get back A right ? And as for B I don't need to do anything to it

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KSSV
KSSV 2016-11-23
doc lscurvefit.

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