Could you help me with FUNCTION syntax

Hi, could you help me please, how to make a function - for example

function [xx,yy,xx1,yy1,a,aa,b,bb]=(x,y,x1,y1)

(this is I tryed and it doesnt work :-( )

I have a points in my code (predefined - x,y,x1,y1) and I want change this points for a function (its mean write my own coordinate of points to the command window). Then I Interpolate and approximate this points by spline and polyfit.

Here is my code syntax (it works good, but I wanna make this like a function).. Thanks for any help, I just learning in Matlab so use simply answer :-)

CODE:

obr = imread('Pokus1.jpg');
obr = obr(:,:,1);
obr = im2double(obr);
figure(1)
imshow(obr,[]);
[a,b]=size(obr);

x=[19.25 ; 217.25 ; 523.25 ; 806.75 ; 1135.25 ; 1345.25 ; 1612.25];
y=[545.75 ; 364.25 ; 155.75 ; 92.75 ; 145.25 ; 256.25 ; 418.25];
x1=[163.25 ; 361.25 ; 778.25 ; 1007.75 ; 1175.75 ; 1409.75];
y1=[572.75 ; 358.25 ; 178.25 ; 200.75 ; 265.25 ; 425.75];

hold on
axis on

plot (x,y,'o');

xx = 1:0.01:b;
yy = spline(x,y,xx);
hold on
plot(x,y,'o',xx,yy, 'LineWidth', 3);

plot (x1,y1,'o');
xx1 = 1:0.01:b;
yy1 = spline (x1,y1,xx1);
hold on
plot(x1,y1,'o',xx1,yy1, 'LineWidth', 3);
hold off

figure(2)
imshow(obr,[]);

p = polyfit(x,y,2);
a = 1:0.01:b;
aa = polyval (p,a);

hold on
axis on
plot(x,y,'o',a,aa, 'LineWidth', 3);

p1 = polyfit(x1,y1,2);
b = 1:0.01:b;
bb = polyval (p1,b);
plot(x1,y1,'o',b,bb, 'LineWidth', 3);
hold off

[Oleg Komarov]

format the code please: http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

[Peter]

I did it :-) Could you help me please??

Answer 1

[Walter Roberson]

The line

function [xx,yy,xx1,yy1,a,aa,b,bb]=(x,y,x1,y1)

needs to have the function name added between the "=" and the "("

Answer 2

[Eric]

First you need to give the function a name. Here I've called it my_function() and you should save it as my_function.m somewhere on the Matlab path.

function [xx,yy,xx1,yy1,a,aa,b,bb]=my_function(x,y,x1,y1)

-Eric

[Peter]

Yeah I did it :-( But it stil doesnt work..

I saved function [xx,yy,xx1,yy1,a,aa,b,bb]=my_function(x,y,x1,y1).

And when I want play function - from command window - for example :

[xx,yy,xx1,yy1,a,aa,b,bb]=my_function(19,545,163,572) i tell me:

??? Output argument "xx" (and maybe others) not assigned during call to "C:\Documents and Settings\blabla...

Do you know please how to write function syntax right??

[Walter Roberson]

That's still the function syntax. An output argument not assigned has to do with the code inside the function.

[Peter]

And could you help me how to fix it? When you look above on my code, how to make function? I would like to delete my own points (x,y,x1,y1) and use the function - write my own points..:-)

Answer 3

[Eric]

I'm not entirely sure what you want this function to do. How about something like this? From the Matlab command prompt:

x=[19.25 ; 217.25 ; 523.25 ; 806.75 ; 1135.25 ; 1345.25 ; 1612.25];
y=[545.75 ; 364.25 ; 155.75 ; 92.75 ; 145.25 ; 256.25 ; 418.25];
x1=[163.25 ; 361.25 ; 778.25 ; 1007.75 ; 1175.75 ; 1409.75];
y1=[572.75 ; 358.25 ; 178.25 ; 200.75 ; 265.25 ; 425.75];

Then in my_function.m:

function [xx,yy,xx1,yy1,a,aa,b,bb]=my_function(x,y,x1,y1)

obr = imread('moon.tif');
obr = im2double(obr);
[a,b]=size(obr);

xx = 1:0.01:b;
yy = spline(x,y,xx);

xx1 = 1:0.01:b;
yy1 = spline (x1,y1,xx1);
p = polyfit(x,y,2);

a = 1:0.01:b;
aa = polyval (p,a);

p1 = polyfit(x1,y1,2);
b = 1:0.01:b;
bb = polyval (p1,b);

return

Then from the command prompt again:

[xx,yy,xx1,yy1,a,aa,b,bb]=my_function(x,y,x1,y1);

You might also want to pass the image in as a variable. Also, I've switched to moon.tif since I don't have your image.

[Peter]

Thank you very much for your time and help :-)