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copied!<p>The problem is that the variable <code>persons</code> isn't accessible inside the function <code>process_store</code>. In Matlab (and most other programming languages) functions can't access variables defined in their calling functions. To understand this better, I recommend having a read of the Wikipedia article on <a href="http://en.wikipedia.org/wiki/Scope_%28computer_science%29" rel="nofollow">levels of scope</a>.</p> <p>You essentially have two options here:</p> <ol> <li><p>Make <code>persons</code> a global variable, both in your workspace and in the function <code>process_store</code>, by using the declaration <code>global persons</code>. I wouldn't recommend this.</p></li> <li><p>Use the function <code>evalin</code> to allow <code>process_store</code> to access variables in its parent workspace.</p></li> </ol> <p>I'd go with option 2 if I were you. It's a little tricky, so let me explain how it works. Let's create a variable <code>persons</code> in the global workspace.</p> <pre><code>>> persons = {'John', 'Jack', 'Jill'}; </code></pre> <p>Now say we have the following function</p> <pre><code>function example() x = input('Give me a variable name: '); disp(x) end </code></pre> <p>What happens if we try to use it?</p> <pre><code>>> example() Give me a variable name: persons Error using input Undefined function of variable 'persons' Error in example (line 2) x = input('Give me a variable name: '); </code></pre> <p>Oh dear. That's because the function <code>example</code> doesn't have access to the global workspace, which is where <code>persons</code> is defined. But instead, we can store the name of the variable we want to access, and then check out its value in the global workspace by using <code>evalin</code>, like this</p> <pre><code>function example() s = input('Give me a variable name: ', 's'); x = evalin('caller', s); disp(x) end </code></pre> <p>Now if we use it:</p> <pre><code>>> example() Give me a variable name: persons 'John' 'Jack' 'Jill' </code></pre> <p>It works as we expected! Great!</p> <h3>Massive disclaimer</h3> <p>There is almost never a good reason to use functions like <code>evalin</code> (or <code>eval</code>, or <code>assignin</code> or any other function that messes around executing strings as code). There's almost certainly a better way of doing what you want to do. But without knowing what it is you're trying to do, it's hard to give you better advice.</p>

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