How can i obtain a nice curve ?

x= [1e3; 1e4; 1e5; 1e6; 1e7];
p=[7.87E-07 1.77E-06 1.72E-06 4.44E-07 5.03E-08];
figure(1)
loglog(x,p)
grid
xlabel('Load Resistance [\Omega]')
ylabel('Peak Power [mW/g^{2}]')

EDIT — Forgot the square brackets ‘[]’ in ylabel.

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Mallouli Marwa 2017-1-15

How can i use spline to loglog(x,p) ?

Star Strider 2017-1-15

You can use interp1 with the 'spline' and loglog options to create the interpolation vector, but it will not produce the curve you want. I already did that without success.

Your best option is to provide a diagram or mathematical model of the system you are measuring, and do a (probably nonlinear) fit to it. (I might be able to develop an equation for the model in the diagram if it has fewer than 5 parameters.)

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Answer 2

John D'Errico 2017-1-14

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https://ww2.mathworks.cn/matlabcentral/answers/320393-how-can-i-obtain-a-nice-curve#answer_250582

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loglog(x,p)
grid on

It seems a decent enough curve to me. You could use a spline to interpolate, or just a low order polynomial, as fit to the logs of your data. Anytime you have data that spans many orders of magnitude, it is a hint to use logs.