Summation of several rows using the if condition

[Sylvie Sanou]

Hello,

I want to write a code that creates a value which is the summation of several rows. I have negative values in my data and I want to ignore those values in the summation. I have run the following code but it is giving me missing values.

local x owe1 owe2 owe3 owe4
foreach x in `x'{
gen loan_1998= owe1+ owe2+ owe3+ owe4 if `x'>0

}

Here is how my data is looking like: it is a survey data and the the value -4 corresponds to a valid skipped.

PUBID	SEX	BDATE_M	BDATE_Y	CV_SAMPLE_TYPE	RACE_ETHNICITY	owe1	owe2	owe3	owe4	owe_1998
96	Male	2982616	1982	Cross-sectional	Non-Black / Non-Hispanic	-4	-4	-4	-4	.
97	Male	2982616	1980	Cross-sectional	Hispanic	-4	-4	-4	-4	.
98	Male	2982616	1980	Cross-sectional	Non-Black / Non-Hispanic	-4	-4	-4	-4	.
99	Male	2982616	1982	Cross-sectional	Hispanic	-4	-4	-4	-4	.
100	Female	2982616	1981	Cross-sectional	Black	-4	-4	-4	-4	.
101	Female	2982616	1981	Cross-sectional	Black	-4	-4	-4	-4	.
102	Female	2982616	1982	Cross-sectional	Hispanic	-4	-4	-4	-4	.
103	Female	2982617	1983	Cross-sectional	Hispanic	-4	-4	-4	-4
104	Female	2982617	1980	Cross-sectional	Non-Black / Non-Hispanic	-4	1500	-4	-4	.
105	Male	2982617	1983	Cross-sectional	Non-Black / Non-Hispanic	-4	-4	-4	-4	.
106	Male	2982617	1981	Cross-sectional	Non-Black / Non-Hispanic	-4	-4	-4	-4	.
107	Female	2982617	1982	Cross-sectional	Non-Black / Non-Hispanic	-4	-4	-4	-4	.
108	Male	2982617	1984	Cross-sectional	Non-Black / Non-Hispanic	-4	-4	-4	-4	.
109	Female	2982616	1982	Cross-sectional	Non-Black / Non-Hispanic	-4	-4	-4	-4	.
110	Female	2982616	1984	Cross-sectional	Non-Black / Non-Hispanic	-4	-4	-4	-4	.
111	Female	2982616	1981	Cross-sectional	Non-Black / Non-Hispanic	-4	-4	-4	-4	.
112	Female	2982616	1984	Cross-sectional	Non-Black / Non-Hispanic	-4	-4	-4	-4	.
113	Male	2982616	1984	Cross-sectional	Non-Black / Non-Hispanic	-4	-4	-4	-4	.
114	Female	2982616	1982	Cross-sectional	Non-Black / Non-Hispanic	-4	-4	-4	-4	.
115	Female	2982617	1984	Cross-sectional	Hispanic	-4	-4	-4	-4	.
116	Male	2982617	1984	Cross-sectional	Black	-4	-4	-4	-4	.

I am wondering if someone can please help me figure out what is wrong?

Thank you for your assistance!