Calculating slope of the log of the dataset

I want to calculate the slope of the log of the given dataset. I have provided the excel data file for which I need to find the slope of the log values. I have done the computation in the attached excel sheet. I need to replicate the same in matlab

Answer 1

[Star Strider]

Please be more specific.

Your entire Excel file consists of:

          NaN          NaN          NaN          370          450          550
          NaN          NaN          NaN          NaN          NaN          NaN
            2            3            4      -1.7472          NaN          NaN
            1            2            4      -3.4969          NaN          NaN

This does not lend itself to any calculations.

[MatLab Code N]

Appologies for the confusion. The value 370,450 abd 550 are the x-values for the slope (which remains same all the time) and 2,3 and 4 and 1,2 and 4 are the two sets of y-values for the slope. If you'd open the excel sheet on excel, column D3 and D4 are calculated based on the formula I wanted to replicate on matlab.

In excel I'm using the formula, -slope(log10(A3:C3),log10(D$1:F$1)).

[Star Strider]

You will have to change these for other Excel files, however this works for the one you posted:

[D,S] = xlsread('Example.xlsx')
x = D(1,~isnan(D(1,:)))
y = D(3:4,1:3)
lx = log(x);
ly = log(y);
B1 = [lx(:) ones(size(x(:)))] \ ly(1,:)';
B2 = [lx(:) ones(size(x(:)))] \ ly(2,:)';
Slope1 = -B1(1)
Slope2 = -B2(1)

producing:

Slope1 =
          -1.74721735782446

Slope2 =
           -3.4968960647425        

Those are the same as in your Excel calculations.

[Star Strider]

My pleasure.

I can only help with the data I have, and I do not even know the structure of those files so I cannot generalise my code for them.

You might find the polyfit (link) and related functions useful.

I will delete my Answer in a few minutes, since it apparently did not solve your larger problem.

[MatLab Code N]

This answer was helpful. I could edit it to serve my purpose.

Thanks.

[Star Strider]

My pleasure.

If my Answer helped you solve your problem, please Accept it!