curve fitting in matlab

Question

I have four curves for four different times as shown below in the figure. I need to draw the curve for time in between the given times e.g., I need to plot the curve for $t= 3$ and $t=10$ in matlab (this is just an example shown in below figure).

Is it possible, if so, please suggest something. A big thank you.

Answer 1

If I interpret your question correctly, you want to plot f(t,x)=sin(t*x) for various values of t and x? Am I right? If so, the following code creates a quite extensive graph with f(t,x) evaluated for many values of t and x, but a few values of t and x are marked.

The command mesh(X,Y,Z) can make 3D plots of {X,Y,Z} data.

clear
close all

f=@(t,x)sin(t.*x);

n=101;

minT=0;
maxT=20;
minX=0;
maxX=1;

T=linspace(minT,maxT,n);
X=linspace(minX,maxX,n);

[T,X]=meshgrid(T,X);

Z=f(T,X);

% the blue mesh plot
mesh(T,X,Z,'MeshStyle','column','EdgeColor','b','FaceAlpha',.2)

xlabel t
ylabel x
zlabel z
title('z=sin(t*x)')

set(gca,'View',[50 70])

% the plot with t=[1 5 11 17] marked
k=[];
for tToFind=[1 5 11 17]
    k=[k find(T==tToFind)];
end

hold on
mesh(T(k),X(k),Z(k),...
    'EdgeColor','r',...
    'FaceAlpha',.2,...
    'MeshStyle','Column',...
    'LineWidth',2)

% the plot with x=[.1 .25 .6 .8] marked
k=[];
for xToFind=[.1 .25 .6 .8]
    k=[k find(X==xToFind)];
end

mesh(T(k),X(k),Z(k),...
    'EdgeColor','g',...
    'FaceAlpha',.2,...
    'MeshStyle','Column',...
    'LineWidth',2)

Please use the Rotate 3D button in the Figure window to rotate the view of the 3D plot, then you will get a better feeling for what is plotted. You might also want to maximise your Figure window. Remember to look at the axis labels, to see where the t- and x-axes are while rotating.