# Unrecognized function or variable 'mexnnz'?

Thank you for reviewing my question! I have been struggling with getting CVX working.
Hope you can give me some help here!

After running cvx_setup, I tried this simple example:
m = 20; n = 10; p = 4;
A = randn(m,n); b = randn(m,1);
C = randn(p,n); d = randn(p,1); e = rand;
cvx_begin
variable x(n)
minimize( norm( A * x - b, 2 ) )
subject to
C * x == d
norm( x, Inf ) <= e
cvx_end

Then I got this error message:
Calling SDPT3 4.0: 56 variables, 22 equality constraints
For improved efficiency, SDPT3 is solving the dual problem.
------------------------------------------------------------

``````  num. of constraints = 22
dim. of socp   var  = 41,   num. of socp blk  = 11
dim. of linear var  = 11
dim. of free   var  =  4 *** convert ublk to lblk------------------------------------------------------------
Status: Error
Optimal value (cvx_optval): NaN
Unrecognized function or variable 'mexnnz'.

Error in checkdepconstr (line 97)
nnzmatold = mexnnz(AAt);

Error in sqlpmain (line 87)
checkdepconstr(blk,At,b,y,rmdepconstr);

Error in sqlp (line 243)
sqlpmain(blk3,At3,C3,b,par,parbarrier3,X03,y0,Z03);

Error in cvx_run_solver (line 46)
[ varargout{1:nargout} ] = sfunc( inputs{:} );

Error in cvx_sdpt3>solve (line 357)
[ obj, xx, y, zz, info ] = cvx_run_solver( @sqlp, blk, Avec, Cvec, b, OPTIONS, 'obj', 'x', 'y', 'z', 'info', settings, 5 ); %#ok

Error in cvxprob/solve (line 422)
[ x, status, tprec, iters, y ] = shim.solve( At, b, c, cones, quiet, prec, solv.settings, eargs{:} );

Error in cvx_end (line 87)
solve( prob );
``````

FYI, this is the CVX version:

cvx_version

## CVX: Software for Disciplined Convex Programming (c)2014 CVX Research Version 2.2, Build 1148 (62bfcca) Tue Jan 28 00:51:35 2020

Installation info:
Path: C:\Users\tcly1\Documents\MATLAB\cvx-rd\cvx
MATLAB version: 9.11 (R2021b)
OS: Windows 10 amd64 version 10.0
Java version: 1.8.0_202
Verfying CVX directory contents:
WARNING: The following files/directories are missing:
C:\Users\tcly1\Documents\MATLAB\cvx-rd\cvx\sedumi.travis.yml
These omissions may prevent CVX from operating properly.
WARNING: The following extra files/directories were found:
C:\Users\tcly1\Documents\MATLAB\cvx-rd\cvx\eg1.m
These files may alter the behavior of CVX in unsupported ways.
Preferences:
Path: C:\Users\tcly1\AppData\Roaming\MathWorks\MATLAB\cvx_prefs.mat