Help: Smooth a curve generated from a group of specified points

Hi,

I have 2 vector of x, y coodinates of points

x=[0 50 935 1870 1935 2805 3740 4675 5610 6545 6746 7480 7911 8415 8590 9004];

y=[300 600 716 892 900 990 1052 1071 1037 934 900 736 600 393 300 0];

length(x)=length(y)=16.

The first curve is generated by plot(x,y).

Because I want to smooth the orginal curve. From x, y vectors, I want to generate x', y' vectors with length(x')=length(y')=101. And the second curve is generated by plot(x',y').

Could someone please help me to do this?

I also created a script to do it, but the result wasn't same as the one I want.

My script:

clc
clear all
x=[0 50 935 1870 1935 2805 3740 4675 5610 6545 6746 7480 7911 8415 8590 9004];
y=[300 600 716 892 900 990 1052 1071 1037 934 900 736 600 393 300 0];
plot(x,y,'-o');
xnew=linspace(x(1),x(end),101);
ynew=spline(x,y,xnew);
figure
plot(xnew,ynew,'--o');

The curve generated by plot(x,y):

The curve generated by plot(x',y'):

The result I want to get:

Khanh.

Answer 1

[Star Strider]

Using interp1 with the 'pchip' method will get you closer:

xi = linspace(min(x),max(x),101);
yi = interp1(x, y, xi, 'pchip');

figure(1)
plot(x, y, '+r')
hold on
plot(xi, yi)
hold off
grid

I experimented with resample, even though it is intended for signal processing. It is definitely not appropriate here.

[Khanh]

Thanks.

[Star Strider]

My pleasure!

Answer 2

[Salaheddin Hosseinzadeh]

Hello Khanh, Please try to use resample rather than spline

doc resample

http://www.mathworks.co.uk/help/ident/ref/resample.html?searchHighlight=resample

Simply resample your x and y value with same factor and then plot them.

Good Luck!

[Khanh]

Thanks.