Finding slope and y intercept

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Rick
Rick 2014-10-20
评论： Venkata 2016-8-17
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

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采纳的回答

Sean de Wolski
Sean de Wolski 2014-10-20
Have you tried the Curve Fitting App (Curve Fitting Toolbox, req'd)
>>cftool
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Andrew Reibold
Andrew Reibold 2014-10-20
If you just use polyfit to get linear data, just take two points from it and do the elementary calculations.
Sean de Wolski
Sean de Wolski 2014-10-20
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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更多回答（2 个）

Torsten
Torsten 2016-8-17
Did you look at the x-value where your "intercept" is between 0.32 and 0.33 ?
Best wishes
Torsten.
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Torsten
Torsten 2016-8-17
The p2-value always refers to x=0.
Thus to get the computed value of 0.3046, you must look at the intercept at x=0, not at x=3.85.
Best wishes
Torsten.
Venkata
Venkata 2016-8-17
Now it makes sense.
Thanks a ton, Torsten.

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Venkata
Venkata 2016-8-17
编辑：Venkata 2016-8-17
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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