# How can i obtain a nice curve ?

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Mallouli Marwa le 14 Jan 2017
Commenté : Star Strider le 15 Jan 2017
Hi
How can i obtain a nice curve (like attached curve or logarithmic scale), when my program is
x= [1e3; 1e4; 1e5; 1e6; 1e7];
p=[7.87E-07 1.77E-06 1.72E-06 4.44E-07 5.03E-08];
plot(x,p)
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### Réponse acceptée

Star Strider le 14 Jan 2017
Modifié(e) : Star Strider le 14 Jan 2017
See if this does what you want:
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
ylabel('Peak Power [mW/g^{2}]')
EDIT Forgot the square brackets ‘[]’ in ylabel.
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Mallouli Marwa le 15 Jan 2017
How can i use spline to loglog(x,p) ?
Star Strider le 15 Jan 2017
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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### Plus de réponses (1)

John D'Errico le 14 Jan 2017
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.
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Mallouli Marwa le 15 Jan 2017
How can i interpolate to obtain a nice curve ?

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