What is the best data structure for mapping a key to an array of values in MATLAB?

I am facing an issue with which data structure to use and when. My use case involves unique keys, each of which will be mapped to an array of values.

'UniqueKey1' -> ['Value1', 'Value2', 1, 2, true];
'UniqueKey2' -> ['Value2', 'Value3', 2, 5, false];
'UniqueKey3' -> ['Value3', 'Value4', 5, 5, true];

I know Struct could be one of the options, but I am worried about the performance when the data size is large (more than 100 rows). Can someone recommend a better alternative in my case?

Answer 1

[Matt J]

Dictionaries are supposed to be faster than structs, but they require a recent Matlab version.

keys="UniqueKey"+(1:3)';

values={ {'Value1', 'Value2', 1, 2, true };
         {'Value2', 'Value3', 2, 5, false};
         {'Value3', 'Value4', 5, 5, true}};
         
 d=dictionary(keys,values)

d =

  dictionary (string --> cell) with 3 entries:

    "UniqueKey1" --> {1x5 cell}
    "UniqueKey2" --> {1x5 cell}
    "UniqueKey3" --> {1x5 cell}

         
 d{"UniqueKey2"}

ans = 1x5 cell array
    {'Value2'}    {'Value3'}    {[2]}    {[5]}    {[0]}

[Tej]

Thanks for the information. In my case, the number of keys is not available. I need to add keys to the dictionary dynamically looping through the backend data. Is it possible to modify the values in the cell array for a given key?

[Matt J]

Sure.

https://www.mathworks.com/help/matlab/matlab_prog/getting-started-with-dictionaries.html

[Tej]

That's helpful. Also, assigning the cell array as the value does not work, as shown below

d = dictionary;
insert(d, 'key1', {'Value1', 'Value2', 1, 2, true})

Error using insert
Dimensions of the key and value must be compatible, or the value must be scalar.

The value is expected to be {{'Value1', 'Value2', 1, 2, true}}. Is there a reason that the value has to be assigned this way?

[Paul]

Try changing to:

d = dictionary;
d = insert(d, 'key1' , { {'Value1', 'Value2', 1, 2, true} } )

d =

  dictionary (string --> cell) with 1 entry:

    "key1" --> {1x5 cell}

[Matt J]

You can also add new keys by direct assignment,

d = dictionary('key1',{10}, 'key2',{20})

d =

  dictionary (string --> cell) with 2 entries:

    "key1" --> {[10]}
    "key2" --> {[20]}

d{"key3"}={'Value1', 'Value2', 1, 2, true}

d =

  dictionary (string --> cell) with 3 entries:

    "key1" --> {[10]}
    "key2" --> {[20]}
    "key3" --> {1x5 cell}