How can I use data from .mat file into spline function?

I used the ginput function to select a lot of points, who were stored into a 'data.mat' file.

I now need to use the x and y coordinates into the spline function, which are saved into 'data.mat', but I don't know how to "call" the coordinates from the 'data.mat' file.

I already loaded the data:

S = load('dados.mat');

And I already have the plot ready, I just don't know how to "call" the x and y values.

x =

y =

xx = linspace(0,500,100);

yy = spline(x,y,xx);

figure;

plot(x, y, 'ro');

hold on;

plot(xx, yy, 'b', 'LineWidth', 1.5);

[SALAH ALRABEEI]

If its name was x before you saved it, then x= data.x same for y

[SALAH ALRABEEI]

sorry

x = S.x

[Hélio Filho]

Hello! Thanks for the answer.

The code I have is this:

while (t <= tf)

mov.CurrentTime=t; frame=readFrame(mov); image(frame); drawnow

tv(i)=t; t=t+dt; i=i+1; title(strcat('Frame ',num2str(i)));

[x(i) ,y(i)]=ginput(1);

end

save 'dados.mat'

S = load('dados.mat');

end

%% interpolação por splines cúbicas

x = S.x;

y = S.y;

I get the "Unable to resolve the name" error.

[SALAH ALRABEEI]

see the comment below by @Sulaymon, he just fix it.

[Stephen23]

@Hélio Filho:

It is much more robust to load into an output variable (which is a scalar structure), just as you wrote in your question:

S = load(...)

and then access the fields of that structure, e.g.:

S.x
S.y

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-structure-array.html

Either way you need to know and use the exact names of the data stored in the .mat file, which you can either get from the structure S (e.g. looking at it in the Variable Viewer or using fieldnames), or without even loading the filedata:

whos -file filename

Your original approach of loading into a structure is much better (it is less liable to bugs and easier to debug):

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Answer 1

[Sulaymon Eshkabilov]

Here is the corrected code:

...

save('data.mat', 'x','y');   % Your variable names called x, y and you need to save them here
load data.mat  
end
xx = linspace(0,500,100);
yy = spline(x,y,xx);
figure;
plot(x, y, 'ro');           % x, y from ginput (data.mat)    
hold on;
plot(xx, yy, 'b', 'LineWidth', 1.5);

[Hélio Filho]

I'm still getting the "Unrecognized function or variable 'x'." at the line where I first use x and y

• yy = spline(x,y,xx);

Could it be I have an error in the data or something?

UPDATE: I did the acquiring the x and y data phase again, and I still get the same error, so it's not the file's problem.

UPDATE: So I fixed it, apparently there's such a thing as a "separator"? I don't know what it is, the text even changes color, and I dont know how I put it there, but basically i had the load before that separator, so it wasn't recognizing it. I pasted it below and I no longer have that error.

Even so, your answer helped me, so thanks!

[Stephen23]

It is much more robust to load into an output variable (which is a scalar structure), just as the question shows:

S = load(...)

and then access the fields of that structure, e.g.:

S.x
S.y

Answer 2

[Sulaymon Eshkabilov]

If all the data of x, y are saved under X, Y names from ginput in a sequenctial order in DATA.mat file.

You can load them and eploy, e.g.:

load DATA.mat
% x, y values will be in the MATLAB workspace
% Your code comes here
xx = linspace(0,500,100);
yy = spline(X,Y,xx);
...
    
    

[Hélio Filho]

Hi!

So what I have is:

while (t <= tf)

mov.CurrentTime=t; frame=readFrame(mov); image(frame); drawnow

tv(i)=t; t=t+dt; i=i+1; title(strcat('Frame ',num2str(i)));

[x(i) ,y(i)]=ginput(1);

end

save 'data.mat'

load data.mat

end

xx = linspace(0,500,100);

yy = spline(X,Y,xx);

figure;

plot(x, y, 'ro');

hold on;

plot(xx, yy, 'b', 'LineWidth', 1.5);

With this I get the 'Unrecognized function or variable 'X'' error. Since I called [x(i), y(i)] at the input function I should be able to call it, or am I wrong?

[Stephen23]

It is much more robust to load into an output variable (which is a scalar structure), just as the question shows:

S = load(...)

and then access the fields of that structure, e.g.:

S.x
S.y