## Summary

A great way to dichotomize variables is with a single short compute command. This is also the fastest way to create multi variable filters.

## How Does it Work?

When the structure `COMPUTE A = B = C`

is used, SPSS will evaluate whether `(B = C)`

is True or False for each case. The outcome variable `A`

will be the following

- If (B = C) is True, A = 1
- If (B = C) is False, A = 0
- If (B = C) can’t be evaluated (due to missing values), A will be a system missing value

A nice extra here is that the outcome variable `A`

is perfect for using with FILTER.

## Multiple Conditions

More complex conditions can be used in a similar vein, such as `COMPUTE FLAG = V1 GT V2 AND V3 = 5.`

. This would mean the following:

- If and only if (V1 is larger than V2) and (V3 is 5) will a case have 1 on
`FLAG`

. If`FLAG`

is used as a filter, only these cases will stay active. - If one or both conditions are not true, ‘FLAG’ is 0.
- If there’s any missing value on V1, V2 or V3, ‘FLAG’ is also missing.
- The logic is demonstrated by the syntax below.

## SPSS Syntax Examples

***1. Create test data.**

data list free/v1 v2.

begin data

1 6 ” 5 3 4 4 3 5 2 6 1

end data.

***2. Flag cases where v1 is greater than (gt) 2.
**

compute flag.1 = v1 gt 2.

***3. Flag cases where both v1 and v2 gt 2.
**

compute flag.2 = v1 gt 2 and v2 gt 2.

exe.