Float rounding incorrectly

[ziophase]

Hi All,

I have a float which I get by adding a few things and dividing them -- a weighted average.

If I log the float value, it gives me 8.250000, but if I log the %.1f value, it gives me 8.2! All my other values that are x.5 return the rounded up value.

float avgRating = totalRating / 4;
NSLog(@"ratings: %f, %f, %.1f", totalRating, avgRating, avgRating);
		
........
The console output is:
ratings: 32.000000, 8.000000, 8.0
ratings: 38.000000, 9.500000, 9.5
ratings: 40.000000, 10.000000, 10.0
ratings: 39.000000, 9.750000, 9.8
ratings: 34.000000, 8.500000, 8.5
ratings: 30.000000, 7.500000, 7.5
ratings: 35.000000, 8.750000, 8.8
ratings: 35.000000, 8.750000, 8.8
ratings: 33.000000, 8.250000, 8.2

Note the last line...

Any ideas?

Cheerio,

Tim

[slahteine]

NSLog(@"ratings: %f, %f, %.1f", totalRating, avgRating, (avgRating + 0.05));

[ziophase]

Originally Posted by slahteine

NSLog(@"ratings: %f, %f, %.1f", totalRating, avgRating, (avgRating + 0.05));

This throws other values out:

float avgRating = totalRating / 4;
NSLog(@"ratings: %f, %f, %.1f", totalRating, avgRating, avgRating+0.05);
...
ratings: 32.000000, 8.000000, 8.1
ratings: 38.000000, 9.500000, 9.6
ratings: 40.000000, 10.000000, 10.1
ratings: 39.000000, 9.750000, 9.8
ratings: 34.000000, 8.500000, 8.6
ratings: 30.000000, 7.500000, 7.5
ratings: 35.000000, 8.750000, 8.8
ratings: 35.000000, 8.750000, 8.8
ratings: 33.000000, 8.250000, 8.3

[ziophase]

Originally Posted by slahteine

NSLog(@"ratings: %f, %f, %.1f", totalRating, avgRating, (avgRating + 0.05));

although if you meant to say 0.005, bravo!

works a treat.

cheerio

[ChrisL]

Are you sure that 8.250000 is the exact value of avgRating? Or is this value itself being rounded to 6 decimal places when it's being logged? If the true value of the variable were 8.24999999 then it would actually be doing the correct thing when rounding to one place.

I'd try putting a breakpoint in your code and inspecting the actual value of avgRating in the debugger, not through a log statement.