Removing Those Many Zeroes after Decimals of a variables

[Neelakanda Krishna]

Dear Stata Members
Consider the variable "income" which has an observation equal to usd140000.0000000007.
As I mainly use excel for data cleaning, I have many such figures and I want to trim (I don't know whether that is the correct word or not) or CONSIDER ONLY 3 DIGITS after the decimal. I thought of using -round-function but is there any function that can remove all the digits (retaining 3) after decimal

[Øyvind Snilsberg]

could you type in Stata dataex income in 1/10 and show us the output in the results window?

[Neelakanda Krishna]

Dear Oyvind Snilsberg. Kindly see the image in SPREADSHEER and in colum B,-13.2 is actually -13.1999999999999. If I import those value into Stata, how will Stata treat it? Will Stata round it off to -13.2 or use -13.199....?If the second is how Stata stores, then I have some issues

[Øyvind Snilsberg]

Stata will probably treat it as a string but you can convert it to numeric, which should round it off to -13.2, by typing,

destring(variable),replace

[Nick Cox]

Most multiples of 0.001 can't be held exactly in binary. 0.500, 0.250, 0.750, 0.125, 0;375, 0.625, 0.875 can; but (e.g.) 0.001 certainly can't, This is often called the problem of precision with many explanations such as

Blog . . . . . . . . . . . . . . . . . . The penultimate guide to precision
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . W. Gould
4/12 http://blog.stata.com/2012/04/02/the-penultimate-
guide-to-precision/

Blog . . . . . . . . . . . . . . . . . . . . Precision (yet again), part II
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . W. Gould
6/11 http://blog.stata.com/2011/06/23/pre...again-part-ii/

Blog . . . . . . . . . . . . . . . . . . . . Precision (yet again), part I
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . W. Gould
6/11 http://blog.stata.com/2011/06/17/pre...-again-part-i/

Blog . . . . . . . . . . . . . . . . . How to read the %21x format, part 2
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . W. Gould
2/11 http://blog.stata.com/2011/02/10/
how-to-read-the-percent-21x-format-part-2/


If you want calculations in any currency to be exact, convert to integers.

If you want to see (e.g.) 3 decimal places, round() is not the answer, but display format is;

[Neelakanda Krishna]

Dear Nick Cox thanks for the reply. I have a general question regarding -format-, that it doesn't change the variable but only make the display in a wider format right?

[Nick Cox]

Changing a display format at most changes what is displayed. It never changes what is stored, that is, held in a variable, scalar, matrix,. macro or characteristic.

See https://www.stata-journal.com/articl...article=dm0067 for more.

Apparent exceptions to this are not changing the display format, but changing or creating a value (or set of values) and using a display format as an argument. For example:

. local show : di %4.3f _pi

. di "`show'"
3.142