How to use the diagonal symbol matrix？

I want to use a diagonal symbol matrix in my code, as in the following:

syms a1 a2 a3
a = diag([a1,a2,a3]);
M = matlabFunction(2*a,'vars',{a});

But there's a problem:

Error using sym/matlabFunction>checkVars

Variable names must be valid MATLAB variable names.

Error in sym/matlabFunction (line 158)

vars = checkVars(funvars,opts);

Answer 1

[Paul]

Need to specify the vars explicitly if defined individually

syms a1 a2 a3
A = diag([a1,a2,a3])

A = 

M = matlabFunction(2*A,'Vars',[a1,a2,a3])

M = function_handle with value:
    @(a1,a2,a3)reshape([a1.*2.0,0.0,0.0,0.0,a2.*2.0,0.0,0.0,0.0,a3.*2.0],[3,3])

Or more compactly

a = sym('a',[1 3])

a = 

A = diag(a)

A = 

M = matlabFunction(2*A,'vars',a)

M = function_handle with value:
    @(a1,a2,a3)reshape([a1.*2.0,0.0,0.0,0.0,a2.*2.0,0.0,0.0,0.0,a3.*2.0],[3,3])

[Walter Roberson]

a = sym('a',[1 3])

a = 

A = diag(a)

A = 

M = matlabFunction(2*A,'vars',{a})

M = function_handle with value:
    @(in1)reshape([in1(:,1).*2.0,0.0,0.0,0.0,in1(:,2).*2.0,0.0,0.0,0.0,in1(:,3).*2.0],[3,3])

[宗宾]

It's working,Thanks!