How can i generate a function using this points?

2018 8 29
2 个回答
回答已采纳
更新时间：2018 8 30
3 次查看（30 天）

0 个投票

If i got x=[1,3,8,25,45,23]; and y=[25,24,13,69,25,75];

4 个评论
显示 2更早的评论 隐藏 2更早的评论

Adam
Adam 2018-8-29
编辑：Adam 2018-8-29
What do you expect the function to do exactly?! Handle exactly that one input, returning that one output and throw an error or crash if you give it any other input?
Or do you mean you want to plot these points as x against y?
Mr. 206
Mr. 206 2018-8-29
编辑：Stephen23 2018-8-29
This is an example where there is a y function depends on the values of x. I don't have such function, i only have points so i want a function so that i can use it for example in the below code.
% Simple curve
x = linspace(0,100,200);
y = cos(x/10)+(x/50).^2 + randn(size(x))/10;
z = smooth1q(y,[]);
plot(x,y,'r.',x,z,'k','LineWidth',2)
% axis tight square
Adam
Adam 2018-8-29
There are an infinite number of functions that could take that one example input and give that output.
Mr. 206
Mr. 206 2018-8-29
Okey for example if i want a polynomial function, can you help me?

请先登录，再进行评论。

请先登录，再回答此问题。

 采纳的回答

Jan
Jan 2018-8-29

1 个投票

x = [1,3,8,25,45,23];
y = [25,24,13,69,25,75];
p = polyfit(x, y, 5)

更多回答（1 个）

0 个投票

Hi Here the solution:
% Your cloud point
x=[1,3,8,25,45,23];
y=[25,24,13,69,25,75];
% calculate a new cloud point that contain the last one
xnew = [1, 1.5 ,3,6,8,25,32,45,31,23];
ynew = interp1( x,y, xnew,'pchip' );
% plot de new values
plot(x,y,'o');hold on;plot( xnew, ynew,'r' )
% polinomios
p = interp1( x,y,'pchip' );

5 个评论
显示 3更早的评论 隐藏 3更早的评论

Mr. 206
Mr. 206 2018-8-30
Thanks for reply. Using this 'pchip' command gives an error "error: interp1: discontinuities not supported for method 'pchip'"
What is your MATLAB version ?
Your cloud point
x=[1,3,8,25,45,23]; y=[25,24,13,69,25,75];
[xtointerpol indx ] = sort(x);
ytointerpol = y(indx);
% calculate a new cloud point that contain the last one
ynew = interp1( xtointerpol,ytointerpol, xtointerpol, 'pchip' );
% plot de new values
close all
% plot(x,y,'+b');hold on;plot( xnew, ynew,'--or' )
plot(x,y,'+b');hold on;
plot( xtointerpol, ynew,'--or' )
% polinomios
p = pchip( xtointerpol,ytointerpol );
Mr. 206
Mr. 206 2018-8-30
Great, Now it is working. Thanks :)
Mr. 206
Mr. 206 2018-8-30
If the x values are not monotonic, then is there any way to handle this?
You can define x values in ascending order with sort.
Then you can order de y values.
[xtointerpol indx ] = sort(x);
ytointerpol = y(indx);

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 Cloud Integrations 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