Why can't I refer to an existing value in stata?

[Tiange Tang]

Dear Stata users,

I just encountered a weird issue where I cannot refer to a value that exists in my dataset. Please see below the picture.

Any help and suggestions will be greatly appreciated.
Thank you so much!

Best,
Tiange

[Nick Cox]

This is a precision issue arising from the fact that Stata at machine level works in binary. A number like 0.1 has no exact binary representation.

Long story short, you need to grapple with the different between double and float, as here

. clear

. set obs 1
Number of observations (_N) was 0, now 1.

. gen ave_lob = 0.1

. list if ave_lob == 0.1

. l

     +---------+
     | ave_lob |
     |---------|
  1. |      .1 |
     +---------+

. list if ave_lob == float(0.1)

     +---------+
     | ave_lob |
     |---------|
  1. |      .1 |
     +---------+

.The keyword is precision and a search of Stata using that keyword will point to several blog posts, short papers and other resources on the topic.

[Tiange Tang]

This is a precision issue arising from the fact that Stata at machine level works in binary. A number like 0.1 has no exact binary representation.

Long story short, you need to grapple with the different between double and float, as here

. clear

. set obs 1
Number of observations (_N) was 0, now 1.

. gen ave_lob = 0.1

. list if ave_lob == 0.1

. l

+---------+
| ave_lob |
|---------|
1. | .1 |
+---------+

. list if ave_lob == float(0.1)

+---------+
| ave_lob |
|---------|
1. | .1 |
+---------+

.The keyword is precision and a search of Stata using that keyword will point to several blog posts, short papers and other resources on the topic.

Thank you soooo much, Nick!

It is super helpful!

Best,
Tiange