How can I save into an struct multiple arrays?

I have two variables. Id and Matrix.

Id : [0,1,2,3]

Matrix : 3600 x 9

I want to save in a structure the ID and the respective matrix.

For example:

ID Matrix

0 Matrix(1:900,:)

1 Matrix(901:1800,:)

2 Matrix(1801,2700:)

3 Matrix(2701:3600,:)

How can I make something like this in a matlab function in Simulink?

[Stephen23]

Use a non-scalar structure:

https://www.mathworks.com/help/matlab/matlab_prog/access-multiple-elements-of-a-nonscalar-struct-array.html

This will be simpler and more efficient than messing around with fieldnames.

Answer 1

[Jalaj Gambhir]

Hi,

I understand you want to save numeric id’s as fields and sub matrices as values, in a struct, given a matrix and a double array of ids.

But the question is confusing in the sense that the representation that you have used seems to be of a table.

If what you want is a struct with fields as 0,1,2 and 3, then having numeric fields in a struct is not possible. You can have a look here, it states that the field for a struct must be a character array or a string scalar. However, you can convert the numeric array to a string array and have alternate representations of the elements as fields using matlab.lang.makeValidName using method followed in the following script:

function result = div(id, matrix) 
    start = 1; 
    string_ids = string(id); 
    valid_fields = matlab.lang.makeValidName(string_ids); 
    rows = size(matrix,1); 
    num_id = floor(rows/length(id)); 
    result = struct; 
    for i = 1:length(id)-1 
        temp_array = matrix(start:start+num_id-1,:); 
        result.(valid_fields(i)) = temp_array; 
        start = start+num_id; 
    end 
    last_array = matrix(start:rows,:); 
    result.(valid_fields(length(id))) = last_array; 
end 

The above function outputs:

result = div(id,matrix);
result = 

  struct with fields:

    x0: [900×9 double]
    x1: [900×9 double]
    x2: [900×9 double]
    x3: [900×9 double]

If you want to store the result as a table, using the representation that you have mentioned in the question, you can use the following function:

function table_ans = div(id, matrix) 
    start = 1; 
    cell_id = num2cell(id'); 
    rows = size(matrix,1); 
    num_id = floor(rows/length(id)); 
    result = {}; 
    for i = 1:length(id)-1 
        temp_array = matrix(start:start+num_id-1,:); 
        result{end+1} = temp_array; 
        start = start+num_id; 
    end 
    last_array = matrix(start:rows,:); 
    result{end+1} = last_array; 
    result = result'; 
    table_ans = table(cell_id,result); 
end   

The above function outputs:

table_ans = div(id,matrix)

table_ans =

  4×2 table

    cell_id        result    
    _______    ______________

      [0]      [900×9 double]
      [1]      [900×9 double]
      [2]      [900×9 double]
      [3]      [900×9 double]