Adding and subtracting variables in a row when some of the variables contain missing values

[tig som]

The 10 observations shown in my dataex are taken from my dataset

The variables X1, X2, X3, X4, and X5 are the different variables used to calculate the variable “value”

The formula for calculating a value = X1 + X2 - X3 - X4 + X5



I needed to calculate this value using the above formula

I used the gen function as follows



gen Calucated_value = X1 + X2 - X3 - X4 + X5

As you can see in my file above, whenever I have missing values in one of my variables, the generated calculated value that is shown in the variable “Calculated value” is not equal to my “value” variable. In other words, whenever I have missing values in one of my variables, the calculated value is missing. I don’t want this to happen, unless all the variables X1, X2, X3, X4, and X5 are missing.



Would you please let me know how to address this issue?

Thank you very much, and looking forward to your advice

[Nick Cox]

Your dataex is intended to be helpful but rendered as a screenshot it is much less helpful than you hope. See advice against screenshots in the FAQ.

If what you want is to treat missings as zeros (which isn't stated) then you could approach the problem like this:

clear 
set obs 3 
set seed 314159265

forval j = 1/3 {
    gen X`j' = cond(runiform() < 0.3, ., runiformint(1,5)) 
}


gen Calculated = cond(missing(X1), 0, X1) + cond(missing(X2), 0, X2) - cond(missing(X3), 0, X3) 

list 

     +-------------------------+
     | X1   X2   X3   Calcul~d |
     |-------------------------|
  1. |  5    5    4          6 |
  2. |  .    1    .          1 |
  3. |  1    2    3          0 |
     +-------------------------+

Alternatively see

help mvencode

[tig som]

Thank you very much Nick Cox.
Ok, I will look at advice against screenshots in the FAQ.

I have some issues with performing forval. In my main dataset, the variable names are not just X1, X2, X3, X4, and X5. I used these names to explain my question easily.
The real names are:
X1= total_payment
X2 = support
X3= fee
X4= dedication
X5 = post_payment

Would you please give me advice on how to write the for value command above which I copy and paste again below, with my real variable names?




forval j = 1/3 {
gen X`j' = cond(runiform() < 0.3, ., runiformint(1,5))
}



Thank you again and looking forward to hearing from you,

[Nick Cox]

I used a loop to set up for myself a data example. I can't see, however, that a loop would help you as you have a mix of + and -. The code is a little tedious but starts with just

 
 cond(missing(total_payment), 0, total_payment)

[tig som]

It worked perfectly. Thank you very much, Nick Cox!!