# How to find a polynomial that best fit with scatter plot?

47 ビュー (過去 30 日間)
Andi 2023 年 5 月 12 日
コメント済み: Andi 2023 年 5 月 14 日
Hi everyone,
I am trying to find a best-fit polynomial equation that works well for my data set (two parameters x, and y).
First, I attempt to fit a polynomial line using Excel (figure attached). The equation shows the best fit with the original scatter plot (the red line is the best fit polynomial line).
However, when I try to estimate values with the best-fit equation, it looks very different from actual data points.
A similar error is observed when I attempt to use the Matlab function polyfilt.
clear all
clc
x=data(:,1);
y=data(:,2);
scatter(x,y,'b')
p = polyfit(x,y,2)
May someone suggets me how i can fix this.
(data is also attached).

サインインしてコメントする。

### 採用された回答

Walter Roberson 2023 年 5 月 12 日

x=data(:,1);
y=data(:,2);
scatter(x,y,5,'.r')
p = polyfit(x,y,2);
eqn = poly2sym(p)
eqn =
xest = linspace(min(x), max(x), 75);
yest = polyval(p, xest);
hold on
plot(xest, yest, '-b');
title(char(vpa(eqn,5)))
##### 9 件のコメント7 件の古いコメントを表示7 件の古いコメントを非表示
Walter Roberson 2023 年 5 月 14 日
The sum of squared error is still pretty high for degree 4, and there are still fairly visible artifacts.
Andi 2023 年 5 月 14 日
True, but if I overestimate, then I am unable to incorporate other parameters that have a time-varying influence on the time series. Therefore, I decided to go with a 4-order polynomial.

サインインしてコメントする。

### カテゴリ

Help Center および File ExchangePolynomials についてさらに検索

### Community Treasure Hunt

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

Start Hunting!

Translated by