How to create a string that depends on user input variables?

Hi,

I am currently writing a script in which data collected from a separate file is used to plot curve fits.

I also need to include the equation used for the curve fit on the plot.

I encountered an issue when attempting to do this with a general polynomial, as the degree of the polynomial is decided by the user.

A shortened version of my code is this:

 data = load('data_1.txt');
 x = data(:,1);
 y = data(:,2);
 d = input('To what degree would you like your polynomial?');
 p = polyfit(x,y,d);
 yfit = polyval(p,x);
 plot(x,y,'bo',x,yfit,'r--')

I need a way to create a string that is the correct form of the equation of the polynomial so that it can be properly displayed on the plot.

For example, if the user chooses degree 2, I need to display the equation "p(1)*x^2 + p(2)*x + p(3)" on the plot.

Is there a way to do this for any value of degree?

Any help is appreciated, thanks.

Answer 1

[Rik]

You can create this text with sprintf and some minor tweaks:

str=sprintf('p(%d)*x^%d +', [1:d;(d-1):-1:0]);
str=strrep(str,'^1','');
str=strrep(str,'x^0 + ','');

[Rik]

@培林 王 is this what you needed?

Answer 2

[Siyu Guo]

Try poly2str function. For example, s = poly2str(p, 'x').

[培林 王]

Well, I can't use this function now and I didn't find it in the toolbx. what's the problem?