CODEWITHSUNDEEP
objective-cnsmutablearraynsarrayaverage
Thomas_LEB
Thomas_LEB

Reputation: 239

Average of a NSArray and store value in a new NSArray

i would like to have the average of my NSArray element and store them in a new array in the following way.

NSArray* number;
NSMutableArray* Average;

[Average objectAtIndex:0]=[number objectAtIndex:0];
[Average objectAtIndex:1]=([number objectAtIndex:0] + [number objectAtIndex:1])/2;
[Average objectAtIndex:2]=([number objectAtIndex:0] + [number objectAtIndex:1] + [number objectAtIndex:2])/3;

i was thinking of doing it using 2 for loops

for (int i =0; i<[number count]; i++){
  for (int j=0; j<i; j++){
    temp+=[number objectAtIndex:j];
  }

[Average addObject: temp/(i+1)];

}

can anyone help me with a more efficient way

thank you

Upvotes: 1

Views: 4315

Answers (1)

Rob
Rob

Reputation: 437917

You only need one loop:

NSArray *numbers = @[@(2.4), @(2.7), @(4.0)];
NSMutableArray *averages = [NSMutableArray array];
double total = 0.0;

for (int i = 0; i < [numbers count]; i++) {
    total += [[numbers objectAtIndex:i] doubleValue];
    [averages addObject:@(total / (i + 1))];
}

or, using fast enumeration:

__block double total = 0.0;

[numbers enumerateObjectsUsingBlock:^(NSNumber *number, NSUInteger idx, BOOL *stop) {
    total += [number doubleValue];
    [averages addObject:@(total / (idx + 1))];
}];

By the way, unrelated to your question, but if you simply wanted to average all the numbers in the numbers array, you could use KVC collection operator:

NSNumber *average = [numbers valueForKeyPath:@"@avg.self"];

Clearly that's only useful if you wanted to average all the numbers in the array, but it's a convenient shorthand in those situations.

Upvotes: 6

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