Finding the maximum elements in an NSArray (or NSMutableArray) - iphone

Question

I am having a bit of trouble navigating around an NSArray.
My array:
Element[0] = "ElementA"
Element[1] = "ElementA"
Element[2] = "ElementA"
Element[3] = "ElementA"
Element[4] = "ElementB"
Element[5] = "ElementC"
Are there any methods in Objective-C that will help me find the "median" element? In this case, the "median" would be "ElementA", or the value that occurs the maximum number of times.
In C# this would be a single call, but I can't find an equivalent in Objective-C.
Many thanks,
Brett

Answer 1

Here's how I'd do it:
NSArray * elements = ...; //your array of elements:
NSCountedSet * counts = [NSCountedSet setWithArray:elements]:
id modeObject = nil;
NSUInteger modeCount = 0;
for (id element in counts) {
if ([counts countForObject:element] > modeCount) {
modeCount = [counts countForObject:element];
modeObject = element;
}
}
NSLog(#"element with highest frequency: %#", modeObject);
An NSCountedSet is an NSMutableSet that also remembers how many times its elements have been added to the array.

Answer 2

Wrote this just for you :)
- (NSString *) findModeString: (NSArray *) array {
NSMutableDictionary *stats = [[NSMutableDictionary alloc] init];
for(NSString *str in array) {
if(![stats objectForKey:str]) {
[stats setObject: [NSNumber numberWithInt:1] forKey:str];
} else {
[stats setObject: [NSNumber numberWithInt:[[stats objectForKey:str] intValue] + 1] forKey:str];
}
}
NSInteger maxOccurrences = 0;
NSString *max;
for(NSString *key in stats) {
if([[stats objectForKey:key] intValue] > maxOccurrences) {
max = key;
maxOccurrences = [[stats objectForKey:key] intValue];
}
}
[stats release];
return max;
}
EDIT: Although my solution works, you should upvote/accept #Dave DeLong's answer, it is much much better.

Answer 3

Couldn't you just use:
[myarray length] /2