plotting fitted curve to a set of data

Hi, I am trying to plot a graph of a certain data set of x and y, which I have no problem with, but also i have to plot a FITTED CURVE to that set of data. I been trying and looking for solution on how to get it on google but this is all i've got so far: plot(x, y, '*r') / hold on / plot(x,y, '-b') / hold off.

however the output is more likely to be a line that connects all the points more than a fitted curve

please anybody have a solution???

thanks

Answer 1

[Jon]

Here is some example code that shows two typical ways of plotting a data set a long with a fitted curve.

% example plotting x,y data and fitted curve

% make example data set (quadratic with some noise added) 
x = 1:10;
y = 2*x.^2 + 3 + 25*rand(1,length(x));

% fit the data
c = polyfit(x,y,2);

% generate fitted curve
xfit = 0:0.1:10;
yfit = polyval(c,xfit);

% plot the original data as symbols and fitted curve as connected line
figure % open a new figure for the plot
plot(x,y,'o',xfit,yfit,'-')
legend({'data','curve-fit'})
title('data and fitted curve')

% alternatively you can use the hold on function and make separate calls to
% the plot function

figure % open a new figure for the plot
plot(x,y,'o'); % plot the data
hold on % set hold on so next curve will go in the same plot
plot(xfit,yfit,'-')
hold off % turn hold off in case there is a later call to the plot function
legend({'data','curve-fit'})
title('data and fitted curve')

[nguyễn gia bảo]

thanks a lot

[Jon]

Does this answer your question? If not please detail what else you are looking for. If this answers your question, please accept this as answered.

[John D'Errico]

+1. I might have answered this question, but I'm not sure what I might have said that Jonathan did not say well already. I suppose there are a couple of possibilities you might explore.

One thing you might do is use the curvefitting toolbox, if you have it. It will offer a fairly wide variety of nonlinear models, splines, etc. You would need to decide on a model then. It cannot do that for you.

Another thing you can do is a spline fit. Again, in the CFT, or in MATLAB itself, you can find interpolating splines. In the CFT, there will also be smoothing splines.

You can also find a variety of simple fitting tools from the pulldown menu on your plot figure. Thus look at Tools/Basic Fitting.