poly2str.m

function p = poly2str(c, x)

% poly2str  Convert a polynomial coefficient vector to a string.
%
% p = poly2str(c) generates a string representation of the polynomial
% whose coefficents are in the vector c.  
% The default variable is 'x', unless otherwise specified by 
% p = poly2str(c, 's').
% The coefficients are approximated, if necessary, by the rational
% values obtained from rat.
%	
% If x has a numeric value and the elements of c are reproduced
% exactly by rat, then eval(poly2str(c)) will return the same value 
% as polyval(c, x).
%
% See also polyval, rat.

if nargin < 2, x = 'x'; end
if all(c == 0), p = '0'; return, end

p = [];
n = length(c);
for d = 0: n-1
   if d > 0
      if c(n-d+1) > 0
         p = [' + ' p];
      elseif c(n-d+1) < 0
         p = [' - ' p];
      end
   end
   if c(n-d) ~= 0
      if d == 1
         p = [x p];
      elseif d > 1
         p = [x '^' int2str(d) p];
      end
      if (abs(c(n-d)) ~= 1) | (d==0)
         if d > 0,
            p = ['*' p];
         end
         [sn, sd] = rat(abs(c(n-d)));
         s = num2str(sn);
         if sd ~= 1, s = [s '/' num2str(sd)]; end
         p = [s p];
      end
   end
end
if n > 0
   if c(1) < 0
      p = ['-' p];
   end
end