Is there any way to use hashtables/hashmaps in matlab? [duplicate]

Answer 1

Depending on how literal your example is, the disp will be a massive overhead (I/O is very slow).

That aside, I believe the quickest way to do a check like this is:

if find(primes==3,1,'first')
    disp('yes');
else
    disp('no');
end

Edit, you could also use any(primes==3) - a quick speed test shows they're approximately equivalent:

>> biglist = 1:100000;
>> tic;for i=1:10000
find(biglist==i,1,'first');
end
toc
Elapsed time is 1.055928 seconds.

>> tic;for i=1:10000
any(biglist==i);
end
toc
Elapsed time is 1.054392 seconds.

Answer 2

Like this?

>> m = java.util.HashMap;
>> m.put(1,'hello,world');
>> m.get(1)
ans =
hello, world

Alternatively, if you want a Matlab-native implementation, try

>> m = containers.Map;
>> m('one') = 1;
>> m('one')
ans =
     1

This is actually typed - the only keys it will accept are those of type char. You can specify the key and value type when you create the map:

>> m =  containers.Map('KeyType','int32','ValueType','double');
>> m(1) = 3.14;
>> m(1)
ans =
  3.14

You will now get errors if you try to put any key other than an int32 and any value other than a double.

You also have Sets available to you:

>> s = java.util.HashSet;
>> s.put(1);
>> s.contains(1)
ans = 
     1
>> s.contains(2)
ans = 
     0