Creating empty cell array with function

function link_set = build_links(link_vectors);

% Use the 'cell' 'and 'size' commands to create an empty cell array the
    % same size as link_vectors, named 'link_set'

    link_set = cell(1,size(link_vectors));

I am working on a project in MATLAB Grader and it has been a while since iv'e used MATLAB. I'm having trouble creating this array and I keep getting the "Not enough input arguments." error. Any help or guidamce would be greatly appreciated.

[AndresVar]

1. "not enough input arguments": your function has 1 argument so you have to call it with 1 input. For example build_links(x), where x is something you defined earlier
2. cell(1,size(...))) will give error. You want to make a cell(size(x))

[Carly Hudson]

function link_set = build_links(link_vectors)
% Take a set of link vectors and augment each with a zero vector representing
% the base of the link
%
% Input:
%
%   link_vectors: a 1xn cell array, each element of which is an mx1 vector
%       from the base to end of a link, as seen in its *local* coordinate
%       frame 
%
% Output:
%
%   link_set: a 1xn cell array, each element of which is a mx2 matrix whose
%       first column is all zeros (representing the base of the link in its
%       local frame) and whose second column is the link vector (end of the
%       link) in its local frame

    %%%%%%%%%%%%%%
    % Use the 'cell' 'and 'size' commands to create an empty cell array the
    % same size as link_vectors, named 'link_set'

    %%%%%%%%%%%%%
    % Loop over the vectors in link_vectors, constructing a matrix whose
    % first column is all zeros and whose second column is the link vector,
    % and saving this matrix in the corresponding column of link_set

end

this is the whole prompt. im just confused because link_vectors is something that already exists. so i dont know why i cant just call it in when i define link_set

[AndresVar]

I see, well here is an example, for n=2, m=3. This function just creates a cell array the same size as the input, which is the first part of what your function should do.

anInput = {[1;2;3],[4;5;6]}; % variable to use as an input
size(anInput)

ans = 1×2

1 2

anOutput = theFunction(anInput); % function call returns an output
size(anOutput) % the function made an output with the same size as the input

ans = 1×2

1 2

function theOutput = theFunction(theInput) % function definition block
    theOutput = cell(size(theInput));
    
    %%% make a matrix
end

Btw to be clear in your actual example: link_vectors is an input, you call build_links, and it returns a copy of link_set.

Answer 1

[KSSV]

It seems you are straight away running the function. You need to provide the inputs to the function and then call the function.

link_vectors = rand(1,3) ; % define your input variables
% now call the function 
link_set = build_links(link_vectors);

[Carly Hudson]

function link_set = build_links(link_vectors)
% Take a set of link vectors and augment each with a zero vector representing
% the base of the link
%
% Input:
%
%   link_vectors: a 1xn cell array, each element of which is an mx1 vector
%       from the base to end of a link, as seen in its *local* coordinate
%       frame 
%
% Output:
%
%   link_set: a 1xn cell array, each element of which is a mx2 matrix whose
%       first column is all zeros (representing the base of the link in its
%       local frame) and whose second column is the link vector (end of the
%       link) in its local frame

    %%%%%%%%%%%%%%
    % Use the 'cell' 'and 'size' commands to create an empty cell array the
    % same size as link_vectors, named 'link_set'

    %%%%%%%%%%%%%
    % Loop over the vectors in link_vectors, constructing a matrix whose
    % first column is all zeros and whose second column is the link vector,
    % and saving this matrix in the corresponding column of link_set

end

this is the whole prompt. im just confused because link_vectors is something that already exists. so i dont know why i cant just call it in when i define link_set