MATLAB: Interpolation with a smooth curve

interpolation

How can I write a script that plots the data and then interpolates it with a smooth curve (plot

the curve too). also find and plot the value of y for t=4.

t 0 0.5 1.0 6.0 7.0 9.0

y 0 1.6 2.0 2.0 1.5 0

Best Answer

https://www.mathworks.com/help/matlab/ref/interp1.html#d120e628896

t = [0 0.5 1.0 6.0 7.0 9.0];
y = [0 1.6 2.0 2.0 1.5 0];
y_when_t_is_4 = interp1(t,y,4);
xx=linspace(t(1),t(end),1000);
yy=interp1(t,y,xx,'spline');  % use whatever method suits you the best
plot(t,y,'o',xx,yy)

Related Solutions

MATLAB: Inserting Elements in middle of 1-D, 2-D, N-D Array

interp1() is suitable for such cases.

X = [1 2 3 4 5];
n_new = 9;
X_new = interp1(linspace(0,1,numel(X)), X, linspace(0,1,n_new))

For a high-dimensional case, you need to specify whether you want to apply it on a single dimension or all the dimensions?

MATLAB: Plotting a smooth curve from points

Direct analytic method using piecewise cublic polynomial. The curve is first-order differentiable, but not second order differentiable (as with sublic spline or result with my first answer using BSFK)

x = [0;3;6;9;12;15];
y = [0;1.9190;-3.2287;3.5133;-2.6825;1];
[xx,is] = sort(x(:));
yy = y(is);
yy = yy(:);
dx = diff(xx);
dy = diff(yy);
y0 = yy(1:end-1);
n = numel(xx)-1;
coefs = [-2*dy./(dx.^3), 3*dy./(dx.^2), 0*dy, y0];
pp = struct('form', 'pp',...
    'breaks', xx(:)',...
    'coefs', coefs,...
    'pieces', n, ...
    'order', 4,...
    'dim', 1);
figure
xi = linspace(min(x),max(x));
yi = ppval(pp,xi);
plot(x,y,'b-o',xi,yi,'r');
xlim([min(x),max(x)])
grid on

Propably this is how John generates his curve

x = [0 1 1.5 2 4];
y = x;

Best Answer

Related Solutions

MATLAB: Inserting Elements in middle of 1-D, 2-D, N-D Array

MATLAB: Plotting a smooth curve from points

Related Question