A dictionary is useful for a fast lookup of values in a larger set. A dictionary is a map that stores data as values, which can be accessed using corresponding unique keys. Each pair of keys and values is an entry.
Before MATLAB R2022b, there is not an official dictionary data type. Though you can use Map Containers as an alternative. It is not very convenient in our daily work. In the version R2022b, the official version is coming. Let’s have a look.
Functions
There are some functions in the dictionary object, like entries, keys, values, types, numEntries, isConfigured, and isKey. The content of each function is as felow:
| Functions | Content |
|---|---|
| entries | Key-value pairs of dictionary |
| keys | Keys of dictionary |
| values | Values of dictionary |
| types | Types of dictionary keys and values |
| numEntries | Number of key-value pairs in dictionary |
| isConfigured | Determine if dictionary has types assigned to keys and values |
| isKey | Determine if dictionary contains key |
Syntax
The syntax is easy just like in Python and other languages.
d = dictionary(keys,values)
d = dictionary(k1,v1,...,kN,vN)
d = dictionary
Let’s take an example. d = dictionary(keys, values) creates a dictionary with specified keys and values. The resulting dictionary d is a 1-by-1 scalar object. If multiple values are assigned to the same key, then only the last of those values are assigned. New assignments to an existing key overwrite the value for that entry.
Example
I use the dictionary data type to store the serial number and the group label of a seismograph. This helps me to sort and find the information more conveniently.
instrGroupSerial = dictionary('590000037','A1', '590000050','A2', '590000059','A3', '590000064','A4',...
'590000066','A5', '590000099','A6',...
'590000102','B1', '590000105','B2', '590000106','B3', '590000111','B4',...
'590000342','B5', '590000343','B6',...
'590000345','C1', '590000351','C2', '590000358','C3', '590000372','C4',...
'590000397','C5', '590000400','C6',...
'590000425','D1', '590000446','D2', '590000450','D3', '590000458','D4',...
'590000472','D5', '590000587','D6',...
'590000075','E1', '590000080','E2', '590000360','E3', '590000894','E4',...
'590000904','E5', '590000964','E6',...
'590001101','F1', '590001170','F2', '590001172','F3', '590001184','F4',...
'590001186','F5', '590001231','F6',...
'590001240','G1', '590001243','G2', '590001300','G3', '590001347','G4',...
'590001366','G5', '590001379','G6');
If you are interested in the dictionary data type, have a try!