Read and Write Using Key Index
When reading from the Map, use the same keys that you have defined and associated with particular
values. Writing new entries to the Map requires that you supply the values to store with a key for
each one.
Note For a large Map, the keys and value methods use a lot of memory as their outputs are cell
arrays.
Read From Map
After you have constructed and populated your Map, you can begin to use it to store and retrieve
data. You use a Map in the same manner that you would an array, except that you are not restricted to
using integer indices. The general syntax for looking up a value (valueN) for a given key (keyN) is
shown here. If the key is a character vector, enclose it in single quotation marks:
valueN = mapObj(keyN);
Start with the Map ticketMap :
ticketMap = containers.Map(...
{'2R175', 'B7398', 'A479GY', 'NZ1452'}, ...
{'James Enright', 'Carl Haynes', 'Sarah Latham', ...
'Bradley Reid'});
You can find any single value by indexing into the Map with the appropriate key:
passenger = ticketMap('2R175')
passenger =
James Enright
Find the person who holds ticket A479GY:
sprintf('
Would passenger %s please come to the desk?\n', ...
ticketMap('A479GY'))
ans =
Would passenger Sarah Latham please come to the desk?
To access the values of multiple keys, use the values method, specifying the keys in a cell array:
values(ticketMap, {'2R175', 'B7398'})
ans =
'James Enright'
'Carl Haynes'
Map containers support scalar indexing only. You cannot use the colon operator to access a range of
keys as you can with other MATLAB classes. For example, the following statements throw an error:
ticketMap('2R175':'B7398')
ticketMap(:)
Read and Write Using Key Index
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