why the these two equal values when comparing gives 0 as result ?

>> fsern(221)

ans =

6.0000

>> infqs(5)

ans =

6

>>infqs(5)==fsern(221)

ans =

0

[Hindu Rajasree]

why its showing result as zero even if the two values are equal pls explain me

[James Tursa]

FYI, MATLAB is actually giving you a clue. Those trailing 0's in the display of 6.0000 mean that there are non-zero digits after that but are not being displayed, whereas the 6 without the trailing 0's mean that the number is 6 exactly.

Answer 1

[Adam Danz]

6.00000001 == 6
ans =
     0

To see if precision is the issue, one or both lines below should be false.

     fsern(221) == 6.0
     infqs(5) == 6.0

also set your output format to 'long'

     format long

[Hindu Rajasree]

but here it is not 6.00000001 my value is exactly 6.0000

[Adam Danz]

Did you confirm that by running the two lines I suggested in the middle of my answer?

[Steven Lord]

No, it's not. It's displayed as 6.0000 but that doesn't mean its stored value is exactly six. Look at how far away from six is it. This will be small but won't be 0.

difference = fsern(221)-6

Close does not count with the == operator. See the "Avoiding Common Problems with Floating-Point Arithmetic" section on this documentation page for more information.

[Hindu Rajasree]

tq for your explaination can you explain bit more clear

[Steven Lord]

>> x = 0.6/0.1
x =
    6.0000

In exact arithmetic, x would be exactly equal to six since six-tenths divided by one-tenth is six.

>> x-6
ans =
  -8.8818e-16

In floating-point arithmetic, 0.6 is not exactly six-tenths and 0.1 is not exactly one-tenth, so 0.6 divided by 0.1 is not exactly six. You can't exactly represent either 0.6 or 0.1 in floating point; you have some roundoff error in each.

>> x == 6
ans =
  logical
   0

x is very close to 6. The == operator doesn't care how close it is. To the == operator x is not exactly equal to 6, so == returns false.

If you want "close enough" to count, compare using a tolerance as shown in the "Compare Floating-Point Numbers" section on this documentation page.

[Adam Danz]

@Hindu Rajasree, to calculate equality when faced with roundoff error, you can follow this example:

A = 6.0; 
B = 0.6/0.1; 

TF = abs(A-B) < 1e4*eps(min(abs(A),abs(B))); 
% True if equal within tolerance
% false otherwise

Answer 2

[Hindu Rajasree]

tq soo much for ur explanation