Extrapolating from linear fit
10 次查看(过去 30 天)
显示 更早的评论
I have a code, and it works, except is there a way to extend the linear fits past the data they are fitted to? Currently, it plots a line over my data. How can I specify the limits of the linear fit (I'd like to extrapolate). Here is my code:
close all
clear
clc
[D,S] = xlsread('C:\PATH\kvsl.xlsx','500K');
one_over_l = D(:,10);
one_over_k = D(:,11);
ballistic_x = one_over_l((1:7),1);
ballistic_y = one_over_k((1:7),1);
diffusive_x = one_over_l((8:17),1);
diffusive_y = one_over_k((8:17),1);
figure(1)
plot(ballistic_x, ballistic_y,'o')
hold on
P = polyfit(ballistic_x,ballistic_y,1);
yfit1 = P(1)*ballistic_x+P(2);
hold on;
plot(ballistic_x,yfit1,'r-.');
Q = polyfit(diffusive_x,diffusive_y,1);
yfit2 = Q(1)*diffusive_x+Q(2);
hold on;
plot(diffusive_x,yfit2,'b-');
plot(diffusive_x, diffusive_y,'x')
grid on
ylabel('1/\kappa (W/m.K)^{-1}')
xlabel('1/L (\mum^{-1})')
0 个评论
回答(2 个)
Bruno Luong
2018-11-9
编辑:Bruno Luong
2018-11-9
" Currently, it plots a line over my data. How can I specify the limits of the linear fit (I'd like to extrapolate)."
You get it all wrong, polyfit returns coefficients, for later usage it doesn't care the interval used for fit. You can plot in larger interval if you want
Instead of
yfit1 = P(1)*ballistic_x+P(2);
which is similar to stock function
yfit1 = polyval(P,ballistic_x);
Simply extend x
minx = min(ballistic_x);
maxx = max(ballistic_x);
dx = 0.1*(maxx-minx);
xextended = [minx-dx, maxx+dx];
yextended = polyval(P,xextended );
plot(xextended, yextended ,'r-.');
0 个评论
另请参阅
类别
在 Help Center 和 File Exchange 中查找有关 Linear and Nonlinear Regression 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!