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Finding slope and y intercept

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Rick
Rick on 20 Oct 2014
Commented: Venkata on 17 Aug 2016
Hello, I was wondering if there is an easy way to find the slope and intercept of a line using MATLAB, like how it is so easy with Excel where you just plot the data and add a trendline, so then it will tell you the slope and intercept. Here is my code
tau = [15, 38, 100, 300, 1200];
CA = [1.5 1.25 1 0.75 0.5];
CA0 = 2;
dCdt = log((CA-CA0)./tau);
plot(log(CA),log((CA-CA0)./tau))
xlabel('ln(C_{A})')
ylabel('ln(C_{A}-C_{A0}/ \tau)')
I have a theory that says ln((CA-CA0)/tau) = ln(k) + alpha(ln(CA)), and I want to find alpha and ln k, which is my slope and intercept, respectively.
Thank you

Accepted Answer

Sean de Wolski
Sean de Wolski on 20 Oct 2014
Have you tried the Curve Fitting App (Curve Fitting Toolbox, req'd)
>>cftool
  3 Comments
Sean de Wolski
Sean de Wolski on 20 Oct 2014
Student Version usually does come with CFT. Try calling:
>>cftool
To see if you do.
Then you can fit arbitrary functions and you don't have to worry about linearizing them to play with polyfit.

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More Answers (2)

Torsten
Torsten on 17 Aug 2016
Did you look at the x-value where your "intercept" is between 0.32 and 0.33 ?
Best wishes
Torsten.
  3 Comments
Venkata
Venkata on 17 Aug 2016
Now it makes sense.
Thanks a ton, Torsten.

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Venkata
Venkata on 17 Aug 2016
Edited: Venkata on 17 Aug 2016
I've used 'cftool' for my data. The intercept is in between 0.32 and 0.33 as can be seen from the figure.
However, the 'p2' value is 0.3046, with 95% confidence bounds.
Please explain me this.

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