You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: demo_constrlasso.m
    path of file: ./repos/SparseReg
    
    the code of the file until where you have to start completion: %% lasso with a linear equality constraint

% set seed
clear;
s = RandStream('mt19937ar','Seed',1);
RandStream.setGlobalStream(s);

% dimension
n = 100;
p = 20;

% truth with sum constraint sum(b)=0
beta = zeros(p,1);
beta(1:round(p/4)) = 0;
beta(ro
    
function handle for projection subproblem)
tic;
%profile on;
[bhat_admm_fh,stats] = lsq_constrsparsereg(X,y,lambda,...
    'method','admm','projC', @(x) x-mean(x));
%profile viewer;
toc;
display(stats.ADMM_iters);

% plot solutions
figure; hold on;
plot(bhat_qp,'rs');
plot(bhat_gurobi,'-b+');
plot(bhat_admm_matlab,'go');
plot(bhat_admm_gurobi,'m*');
plot(bhat_admm_fh,'kv');
legend