Extrapolating from linear fit

31 次查看（过去 30 天）
Benjamin Cowen
Benjamin Cowen 2018-11-9
编辑： Bruno Luong 2018-11-9
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})')

请先登录，再回答此问题。

回答（2 个）

madhan ravi
madhan ravi 2018-11-9
编辑：madhan ravi 2018-11-9
Bruno Luong
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-.');

类别

在 Help Center 和 File Exchange 中查找有关 Linear and Nonlinear Regression 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by