Create structs with different number of columns

Hi.

Assume that I have a parameter n, that has no constant value.

I want to cretae a single structure with n columns and m rows (m is constsnt) in each iteration of a loop. How can I do this? Note that in each loop, the parameter n is changed, so, the structures have no constant column.

Thanks in advance.

Answer 1

[Walter Roberson]

This is not possible if you are referring to struct array and columns refers to the second dimension. For example if you had

s = struct('hello', 5);
s(1,5).hello = true;

Then you could not say that for s(2,:) you only want 3 columns.

You could store each struct inside a cell array.

[civil tech]

Thank you.

My exact question can be seen as an example below:

Assume that, n = 4. If the names of fields have been defined before as (a,b,c,d), it means that the structure STR has four columns of STR.a, STR.b, STR.c and STR.d.

My problem is that, the n is not constant. Therefore, I can't define (a,b,..) because I don't know how many names is needed for the STR.

[Walter Roberson]

That question is incorrect. That is a scalar struct with four fields.

If you do not know n ahead of time then

fn = cellstr(char(randi(26,n,10)+'a'-1)))

Now you have n different field names and can assign to them using dynamic fields

s.(fn{K}) = "this is field " + K

[civil tech]

Many thank. What is K here?

[Walter Roberson]

When you want to access the K'th field, then fn{K} holds its name.

The code might be rather different if you had a small maximum bound on n making it practical to define allowed field names in advance

[civil tech]

Thank you so much.