1 files changed, 24 insertions, 12 deletions
diff --git a/macros/polyval.sci b/macros/polyval.sci
index bcd5dfb..0ec7a82 100755
--- a/macros/polyval.sci
+++ b/macros/polyval.sci
@@ -1,15 +1,28 @@
 function [y, delta] = polyval(p,x,S,mu)
+//y = polyval(p,x) returns the value of a polynomial of degree n evaluated at x. The input argument p is a vector of length n+1 whose elements are the coefficients in descending powers of the polynomial to be evaluated.
+//x --can be a matrix or a vector. In either case, polyval evaluates p at each element of x.
+//[y,delta] = polyval(p,x,S) uses the optional output structure S generated by polyfit to generate error estimates delta.
+//delta --is an estimate of the standard deviation of the error in predicting a future observation at x by p(x).
+//               If the coefficients in p are least squares estimates computed by polyfit, and the errors in the data input to poly//               if it are independent, normal, and have constant variance, then y±delta contains at least 50% of the
+//                  predictions of future observations at x.
 
-// Check input is a vector
-if ~(isvector(p) | isempty(p))
-    error(message('polyval:InvalidP'));
+//y = polyval(p,x,[],mu) or [y,delta] = polyval(p,x,S,mu) use ˆx=(x−μ1)/μ2 in place of x. In this equation, μ1=mean(x)     //      and μ2=std(x). The centering and scaling parameters mu = [μ1,μ2] is optional
+
+//EXAMPLES:
+//p = [3 2 1];
+//y=polyval(p,[5 7 9])
+//EXPECTED OUTPUT:
+//y=  86  162  262
+
+if ~(isvector(p) | isempty(p))  // Check input is a vector
+    error('polyval:InvalidP');
 end
 
 nc = length(p);
-if isscalar(x) & (argn(2) < 3) & nc>0 & isfinite(x) & all(isfinite(p(:)))
+if isscalar(x) & (argn(2) < 3) & nc>0 & (abs(x)<%inf) & and(abs(p(:))<%inf)
     // Make it scream for scalar x.  Polynomial evaluation can be
     // implemented as a recursive digital filter.
-    y = filter(1,[1 -x],p);
+    y = filter(1,[1 -real(x)],p);
     y = y(nc);
     return
 end
@@ -28,9 +41,9 @@ end
 
 if argn(1) > 1
     if argn(2) < 3 | isempty(S)
-        error(message('polyval:RequiresS'));
+        error('polyval:Requires S');
     end
-    
+
     // Extract parameters from S
     if isstruct(S),  // Use output structure from polyfit.
       R = S.R;
@@ -39,7 +52,7 @@ if argn(1) > 1
     else             // Use output matrix from previous versions of polyfit.
       [ms,ns] = size(S);
       if (ms ~= ns+2) | (nc ~= ns)
-          error(message('polyval:SizeS'));
+          error('polyval:SizeS');
       end
       R = S(1:nc,1:nc);
       df = S(nc+1,1);
@@ -59,12 +72,11 @@ if argn(1) > 1
     E = V/R;
     e = sqrt(1+sum(E.*E,2));
     if df == 0
-        warning(message('polyval:ZeroDOF'));
-        delta = Inf(size(e));
+        warning('polyval:ZeroDOF');
+        delta = %inf(size(e));
     else
         delta = normr/sqrt(df)*e;
     end
-    delta = reshape(delta,siz_x);
+    delta = matrix(delta,siz_x);
 end
 endfunction
-