How to index the value returned by a Map

I'm new to MATLAB so please help me out here.

I have a containers.Map that contains cell arrays. I want to get one of the cell arrays and immediately index an item from it.

I tried simply putting the curly braces after the Map's key index and got this error message:

>> stats('u_est')

ans =

  1×5 cell array

    {[525]}    {[0.9834]}    {[-0.0261]}    {[-1.0166]}    {[1.0009]}

>> stats('u_est'){2}
Error: Indexing with parentheses '()' must appear as the last operation of a valid indexing expression.

Obviously I can do it by assigning a new variable but I think there must be a way to do it directly:

>> values = stats('u_est');
>> values{2}

ans =

    0.9834

Also, what does it mean by "Indexing with parentheses '()' must appear as the last operation of a valid indexing expression"?

thanks

[Tobias Ohrmann]

@Bill Tubbs I have exactly the same problem, did you manage to solve it? Defining a new variable seems very laborious here..

[Bill Tubbs]

No. As far as I know, this kind of 'chained expression evaluation' is an inherent non-feature of MATLAB. The only solution I know is to switch to another language such as Python that parses all the sub-components of an expression with a consistent set of rules and can thus handle compound operations on any objects of valid type.

Answer 1

[KSSV]

YOu have to use

u_est = values{2} ; 

For arrays the indexing is done using (), for cells indexing is done using {}.

[Bill Tubbs]

I'm trying to get the value directly from stats without having to create a new variable! (See first code example).

[KSSV]

If your cell array is C, you can access any value from it using: C{1}, C{2}, ..C{i},

[Bill Tubbs]

Thanks but I am asking if it is possible to get a cell array from a Map and immediately index an item from it. Or is this impossible to do in one statement? If you look at the second code segment it shows that I know how to do it in two steps. The question is can I do it in one? Like this:

stats('u_est'){2}

[Bill Tubbs]

Basically I'm trying to do this in MATLAB:

>>> stats = {'u_est': [525, 0.9834, -0.010]}                                              
>>> stats['u_est'][1]                                                                     
0.9834