A strange arithmetic error in R (maybe a bug)

On 18 Feb 2017, at 05:18, T. Zhang <tz05 at me.com> wrote:

Hello,

Today I happened to notice a strange error in R. If you type (2.01-0.06)==1.95, output from R is ?FALSE?, which is wrong. But if you type (1.01-0.06)==0.95, output is ?TRUE?, which is correct. I tested this in two systems: R 3.3.2 in my iMac and R 3.2.0 on my school?s Linux server. Both gave same outputs. As shown in the following:

2.01-0.06

[1] 1.95

(2.01-0.06)==1.95  # should be TRUE; output is wrong

[1] FALSE

1.01-0.06

[1] 0.95

(1.01-0.06)==0.95  # should be TRUE; output is correct

[1] TRUE

(2.01-0.06)>1.95  # should be FALSE; output is correct

[1] FALSE

(2.01-0.06)<1.95  # should be FALSE; output is wrong

[1] TRUE

Similar errors could be found with simple alterations of the above inputs, such as:

5.533-5.412

[1] 0.121

(5.533-5.412)==0.121  # should be TRUE; output is wrong

[1] FALSE

2.533-2.412

[1] 0.121

(2.533-2.412)==0.121  # should be TRUE; output is correct

[1] TRUE

Could any of you test whether you have same outputs as mine? And does anyone know what is wrong with these? My guess is that R has a bug in processing double numbers. Thanks!

TZ