Trouble with format command changing the value-CodePudding

I first applied destring to an ID variable (with 17 digits). They are destrung but then they are shown in scientific notation. So I tried the command format .0f. Now all digits are shown but the last 2-3 digits are now changed.enter image description here

CodePudding user response：

Stata can only hold numeric variables with up to 16 digits.

Your best option is probably to keep the ID as a string.

The command format only affects how a data point is displayed to humans, not how it is actually stored.

CodePudding user response：

This is to complement the answer by @TheIceBear.

format never changes values. The problem is that your string is too big even for its numeric equivalent to be held exactly in a double, except occasionally.

clear 
set obs 5
gen id = 17*"9" in 1 
replace id = 16*"9"   "6" in 2 
replace id = 16*"9"   "2" in 3 
replace id = 15*"9"   "88" in 4 
replace id = 15*"9"   "84" in 5 
format id  s 
destring id, gen(nid)
format nid  .0f 
list  

      ---------------------------------------- 
     |                id                  nid |
     |----------------------------------------|
  1. | 99999999999999999   100000000000000000 |
  2. | 99999999999999996   100000000000000000 |
  3. | 99999999999999992   100000000000000000 |
  4. | 99999999999999988    99999999999999984 |
  5. | 99999999999999984    99999999999999984 |
      ----------------------------------------