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How to index the value returned by a Map

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Bill Tubbs
Bill Tubbs on 4 Feb 2020
Commented: Bill Tubbs on 19 Mar 2020
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
  2 Comments
Bill Tubbs
Bill Tubbs on 19 Mar 2020
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.

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Answers (1)

KSSV
KSSV on 4 Feb 2020
YOu have to use
u_est = values{2} ;
For arrays the indexing is done using (), for cells indexing is done using {}.
  4 Comments
Bill Tubbs
Bill Tubbs on 4 Feb 2020
Basically I'm trying to do this in MATLAB:
>>> stats = {'u_est': [525, 0.9834, -0.010]}
>>> stats['u_est'][1]
0.9834

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