Nesting function trouble with undefined variable

Trying to code a simple nesting function and I can't understand why I get an undefined function or variable warning for 'a'

    function [Y] = nesty(d,e)
Y(d,e)=2*a;
nestmini
    function [a] = nestmini(d,e)
        a=d+e;
    end
 end

Answer 1

[Walter Roberson]

function [Y] = nesty(d,e)
    a = nestmini;
    Y(d,e)=2*a;
    function [a] = nestmini(d,e)
        a=d+e;
    end
 end

Remember, the variable named as output in a function is a dummy variable that is not assigned outside the function

[aldburg]

Thank you, I apologize if my questions seem trivial.

I tried running the code and I got an error

Not enough input arguments.

    Error in nesty/nestmini (line 5)
            a=d+e;

    Error in nesty (line 2)
        a = nestmini;

[Stephen23]

@aldburg: KL gave you the correct solution already. The above answer is buggy, as it omits to call the nested function with the input arguments that you have defined it with:

function Y = nesty(d,e)
  a = nestmini(d,e);
  Y(d,e) = 2*a;
  function a = nestmini(d,e)
      a = d+e;
  end
end

Although in that case there is absolutely no point in having written nestmini as a nested function, and nestmini could just be a local function. Perhaps you meant to pass d and e via the common workspace rather than as input arguments, which really makes use of nestmini being a nested function:

function Y = nesty(d,e)
  a = nestmini();
  Y(d,e) = 2*a;
  function a = nestmini()
      a = d+e;
  end
end

Both of these work: I tested them.

[aldburg]

I slightly modified the code and I got it to work. Quick question, when my code is Y(d,e) I get an answer that is 2X1 and when I simply use Y=... I get a 1X1 answer. What gives?

function [Y] = nesty(d,e)
    Y=2*nestmini(d,e);
    function [a] = nestmini(d,e)
        a=d+e;
    end
 end

[Stephen23]

@aldburg:

• Y=... defines a totally new variable with the name Y. It has the size of whatever the RHS has.
• Y(d,e)=... uses indexing to allocate values into the selected elements of Y. If Y does not exist before that indexing then MATLAB creates Y and fills the unindexed elements with zero.

The introductory tutorials teach these kind of basic MATLAB concepts, such as defining variables and using indexing, and are highly recommended for all beginners:

https://www.mathworks.com/help/matlab/getting-started-with-matlab.html

[aldburg]

Thanks for explaining that. I will start that once I finish my courses for the quarter. I am learning Matlab to help with my composite mechanics homework.

Answer 2

[KL]

You're passing d,|e| to nesty function but you're using a on the right hand side of the equation. Do not expect matlab to call the nestmini function for you.

If you want to use the function return directly, try something like,

 Y(d,e) = 2*nestmini(d,e);