MATLAB: How to do a spline and divide the spline into points of equal distance

linearspacespline

Hey everybody,

I have a problem concerning my bachelors Thesis and I don't really know what I have to do here…

The task is the following: I want to create a cubic spline through a couple of points, lets say 4 points and have the spline in hundred points of equal distance.

I don't know how to do this, but is there a possibility to to it with one of these functions?

s = spline(x,y,xq)

pp = spline(x,y)

So task is the following:

4 points
100 points inbetween the first and the last one and have them written in an excel file

I need that to do some automatic positioning stuff in a project.

Big thank you for your help in advance!

Johnny

Best Answer

See attached demos.

Related Solutions

MATLAB: Spline fitting a set of data

Try my demo:

% Demo to show spline interpolation.
% Clean up / initialize
clc; 
close all; 
clear all; 
workspace; % Display workspace panel.
% Create the original knot points.
x = 1:10;
y = rand (10,1);
% Plot it and show how the line has sharp bends.
plot(x, y, '-sr', 'LineWidth', 2);
set(gcf, 'Position', get(0,'Screensize')); % Maximize figure.
% Use splines to interpolate a smoother curve,
% with 10 times as many points,
% that goes exactly through the same data points.
samplingRateIncrease = 10;
newXSamplePoints = linspace(1, 10, 10 * samplingRateIncrease);
smoothedY = spline(x, y, newXSamplePoints);
% Plot smoothedY and show how the line is
% smooth, and has no sharp bends.
hold on; % Don't destroy the first curve we plotted.
plot(newXSamplePoints, smoothedY, '-ob');
title('Spline Interpolation Demo', 'FontSize', 20);
legend('Original Points', 'Spline Points');
% Mathworks Demo code from their Help
% x = 0:10;
% y = sin(x);
% xx = 0:.25:10;
% yy = spline(x,y,xx);
% plot(x,y,'o',xx,yy)

MATLAB: How can plot with smooth line

With your data, my demo would become this:

% Create the original knot points.
xInitial = [1.6 1.1 .6 .1 .4 .9 1.4 1.9];
yInitial = [1 1.5 2 2.5 3 3.5 4 4.5];
lengthX = length(xInitial);
% flip sideways so there is only 1 y for every x
x = yInitial;
y = xInitial;
% Plot it and show how the line has sharp bends.
plot(x, y, '-sr', 'LineWidth', 2);
grid on;
set(gcf, 'Position', get(0,'Screensize')); % Maximize figure.
% Use splines to interpolate a smoother curve,
% with 10 times as many points,
% that goes exactly through the same data points.
samplingRateIncrease = 10;
newXSamplePoints = linspace(min(x), max(x), lengthX * samplingRateIncrease);
smoothedY = spline(x, y, newXSamplePoints);
% Now flip back
ySmooth = newXSamplePoints;
xSmooth = smoothedY;
% Plot smoothedY and show how the line is

% smooth, and has no sharp bends.

hold on; % Don't destroy the first curve we plotted.

plot(newXSamplePoints, smoothedY, '-ob');
title('Spline Interpolation Demo', 'FontSize', 20);
legend('Original Points', 'Spline Points');
figure;
plot(xInitial, yInitial, '-sr', 'LineWidth', 2);
% Plot smoothedY and show how the line is
% smooth, and has no sharp bends.
hold on; % Don't destroy the first curve we plotted.
plot(xSmooth, ySmooth, '-ob');
grid on;

You can also use a Savitzky-Golay filter to smooth curves, and I attach a demo for that.

Best Answer

Related Solutions

MATLAB: Spline fitting a set of data

MATLAB: How can plot with smooth line

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