write equation automatically and create a file which save the constant term of the equation

Hi all! I have a script for plot data. My script is:

    for k=159:100:2048

     ix=isfinite(LOGIR(:,k)); 
     x=XMEAN(ix);
     y=LOGIR(ix,k); 
     idx=[1:14]

    p=polyfit(x(idx),y(idx),1);
    yfit=polyval(p,x);

    figure(k);
    plot(x(idx),y(idx),'.',x,yfit,'r')
    gtext(['y=',num2str(p(1)),'x+',num2str(p(2))])
    xlabel('airmass')
    ylabel('logirradiance')

    print(sprintf('Figure(%d).bmp',k), '-dbmp')

    end

I want the equation to appear automatically on the graph and not I place each one. Also, I want to create a file which will save the constant term of each equation. How can I do this?

Thank you!

Answer 1

[dpb]

...I want the equation to appear automatically on the graph and not I place each one.

Use text instead of gtext You'll have to use some pre-knowledge of what your curves look like to put it near the line where it doesn't interfere or pick a position known to be out of the way (like upper left or lower right).

xlab=some_x_position_in axes coordinates;
ylab=same_for_y;
text(x,y,num2str('y=%0.3f*x+%0.3f',p)

_ ...create a file which will save the constant term of each equation..._

Open the file before starting the loop and write each p(2) when it's been calculated.

fid=fopen('Yourdesiredfilename','wt');
for ...
  ...
  fprintf(fid,'%f\n',p(2));
end
fid=fclose(fid);