Fast access to a MATLAB array of structs based on its id

Question

I have a Matlab struct:

a(1).x=54.23; a(1).y=2.3; a(1).col=32.221; a(1).id=1;
a(2).x=5.23; a(2).y=3.3; a(2).col=2.221; a(2).id=2;

... and so on. Now i want to access the struct in a having id 73. I can think of doing a for loop but the thing is i have to access elements of array a several times like this based on id. Wat is the fastest data structure available for this purpose? Python like dictionary may work but i am not sure ow to implement it. Pointing out some code examples would be very helpful.

Actually id can be any integer. id may not correspond to the element number in the array. — user_1_1_1, Apr 07 '17 at 02:04
Then you probably want a [map container](https://www.mathworks.com/help/matlab/map-containers.html) — sco1, Apr 07 '17 at 02:12

score 1 · Accepted Answer · answered Apr 07 '17 at 02:13

Try this:

id=[a.id];
a(id==73)

It's not as efficient as a dictionary, but if it's fast enough for your purposes it's not worth looking further.

The a.id part evaluates to a comma-separated list of id values, which are concatenated in an array that you can then use for lookup.

Fast access to a MATLAB array of structs based on its id

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