MATLAB: Can’t find the syntax errors

MATLABprogramming

I am using MATLAB, SeduMi and YALMIP to implement the algorithm published here. I know I have SeDuMi and YALMIP installed correctly. Before implementing that complicated algorithm, I wanted to use the same approach on an easier problem. With that in mind I tried the code that below, but I get syntax errors. Please show me how to fix the errors. If you can get it working that's even better. The syntax errors are:
  • Keyword for is underlined red with the message: "Invalid use of keyword."
  • norm(residulas,Inf)); has the right most ')' underlined red with the message:"Parse error at ')': usage might be invalid MATLAB syntax."
  • Keyword end is underlined red with the message: "Parse error at END: usage might be invalid MATLAB syntax."
addpath(genpath('C:\Program Files\MATLAB\R2010b\toolbox\yalmip'))
path(path,'D:\Documents and Settings\My Documents\MATLAB\SeDuMi_1_1')
path(path, 'D:\Documents and Settings\My Documents\MATLAB\SeDuMi_1_1\convr')
xvals = 1:0.1:7;
yvals = -xvals.^2+8*xvals-15.5;
residuals = zeros(length(xvals));
% a, w, phi, c  are parameters to be optimized
a = sdpvar(1,1);
w = sdpvar(1,1);
phi  = sdpvar(1,1);
c = sdpvar(1,1);
delta_step = sdpvar(4,1);
options = sdpsettings('solver','sedumi','usex0',1,'verbose',1);
assign(a,-10.58);
assign(w,0.47);
assign(phi,1.2);
assign(c,-9.87);
% determine values of a, w, phi, c that give a minimax 
% approximation of (yvals, xvals) using   y = a*cos( w*x + phi) + c
% BTW:     It seems the solution is  y = -10.6072*cos(0.4729*x+1.25)-9.9049
constraints = [ -11<=a<=-9, 0.35<=w<=0.7, 0.8<=phi<=1.25, -11<=c<=-6,...
   norm(delta_step,2)<=0.04 ];
% 2nd argument of solvesdp is a for loop followed by norm(residuals,inf)
solvesdp(constraints,...
for k=1:length(xvals)
   xval=xvals(k);
   yval=yvals(k);
   % gradient of (a*cos( w*x + phi) + c) WRT (a,b,phi,c)
   gradient = [cos(w*xval)+phi,-a*xval*sin(w*xval)+phi,...
      -a*sin(w*xval)+phi,1];   
   step=gradient*(delta_step);
   residuals(k)=yval-(a*cos(w*xval+phi)-c)+step;
end
norm(residuals,Inf));
solution = [double(a),double(w),double(phi),double(c)];

Best Answer

Thank you for the clarification. Take a look at these lines, towards the bottom of your code:
 solvesdp(constraints,...
 for k=1:length(xvals)
Obviously, there should be something in between these lines, to close the parentheses in the solvesdp function. After that, you can write a for loop and it should work correctly.
What I mean is, you need to write your for loop separately, outside the solvedsp function call. You might need to rework the function definition so that it expects the correct thing. Make a variable that is the result of the for loop or something, and pass that variable to the function.
Alan Weiss
MATLAB mathematical toolbox documentation
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