Plot best fit line in log-space & get slope
40 visualizaciones (últimos 30 días)
Mostrar comentarios más antiguos
newbie9
el 27 de Jul. de 2019
Comentada: Angie Brulc
el 7 de Mzo. de 2022
I am trying to determine the slope of the best-fit line in log space, and plot the best-fit line as a visual check. It needs to be a line, not a curve (I understand that the misfits could be very large in logspace). Below is an example with xy data and polyfit attempts (and plot included). Thanks for any help
x = [7.94, 16.23, 32.92, 66.8, 135.52, 274.93, 557.78, 1131.59, 2295.72, 4657.46];
y = [134000, 102000, 31000, 11000, 2600, 990, 40, 10.41, 3.48, 1.037];
scatter(x,y, 'DisplayName', 'MyData')
set(gca,'xscale','log')
set(gca,'yscale','log')
hold on
grid on
box on
axis equal
p = polyfit(log10(x), log10(y), 1);
z = polyval(p, log10(x));
loglog(x, log10(z), 'DisplayName', 'Try1');
loglog(x, z, 'DisplayName', 'Try2');
z2 = polyval(p, x);
loglog(x, z2, 'DisplayName', 'Try3');
loglog(x, log10(z2), 'DisplayName', 'Try4');
legend
0 comentarios
Respuesta aceptada
Star Strider
el 27 de Jul. de 2019
You are regressing ‘log10(x)’ against ‘log10(y)’ so you need to give the appropriate information to both polyfit and polyval:
Bp = polyfit(log10(x), log10(y), 1);
Yp = polyval(Bp,log10(x));
figure
plot(log10(x), log10(y), 'pg')
hold on
plot(log10(x), Yp, '-r')
hold off
grid
producing this plot:
The slope is -2.0182.
4 comentarios
Más respuestas (1)
newbie9
el 3 de Ag. de 2019
1 comentario
Angie Brulc
el 7 de Mzo. de 2022
Hello,
I'm a random student working on processing data for a lab and just wanted to let you know this was incredibly helpful to me. Thank you!
Ver también
Categorías
Más información sobre Get Started with Curve Fitting Toolbox en Help Center y File Exchange.
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!