Hi.  Long time SPSS Statistics user with a bit of a strange question.

Recently, I ran across a web page that contained an example showing a "COMPUTE" statement that contained two equals signs.   It was something like "COMPUTE x = y = z".  This was new to me however, I was in a rush so didn't mentally land on it.  Coming back to it now and I can't seem to find any reference to the hows/whys of this application in any of my SPSS documentation nor on the web.

Can somebody point me to information on what this COMPUTE format means?

Thanks in advance.

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Scott Terry
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#SPSSStatistics

Thanks Jon and Rick.  This will be very helpful.

Regards!

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Scott Terry
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Original Message:
Sent: Tue April 13, 2021 11:53 AM
From: Jon Peck
Subject: COMPUTE Syntax Containing Two "Equals" Signs

The equals sign has two different roles: assignment and test for equality.  In your example, it is testing equality of y and z and assigning the result to x.  It would be clearer if written as

compute x = y eq z.

The result will be 0 or 1 depending on the outcome of the test.

--

Jon K Peck
jkpeck@gmail.com

It's a boolean evaluation; returns 0 if false and 1 if true. Here 1 if y = z, else 0 (or sysmis if args missing).

data list free /y z.
begin data.
1 2
1 1
end data.
compute x = y = z.
list.
​

I'll look in the Command Syntax Reference in a couple of places and see if that's mentioned.

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Rick Marcantonio
Quality Assurance
IBM
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Thanks Rick.  Very clear.

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Scott Terry
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Original Message:
Sent: Tue April 13, 2021 11:59 AM
From: Rick Marcantonio
Subject: COMPUTE Syntax Containing Two "Equals" Signs

It's a boolean evaluation; returns 0 if false and 1 if true. Here 1 if y = z, else 0 (or sysmis if args missing).

data list free /y z.begin data.1 21 1end data.compute x = y = z.list.​

I'll look in the Command Syntax Reference in a couple of places and see if that's mentioned.

------------------------------
Rick Marcantonio
Quality Assurance
IBM
------------------------------

You're welcome. Just FYI - The help refers to these as "logical expressions." Cf Logical Expressions


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Rick Marcantonio
Quality Assurance
IBM
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Original Message:
Sent: Mon April 19, 2021 09:03 AM
From: Scott Terry
Subject: COMPUTE Syntax Containing Two "Equals" Signs

Thanks Rick.  Very clear.

------------------------------
Scott Terry
------------------------------


Original Message:
Sent: Tue April 13, 2021 11:59 AM
From: Rick Marcantonio
Subject: COMPUTE Syntax Containing Two "Equals" Signs

It's a boolean evaluation; returns 0 if false and 1 if true. Here 1 if y = z, else 0 (or sysmis if args missing).

data list free /y z.begin data.1 21 1end data.compute x = y = z.list.​

I'll look in the Command Syntax Reference in a couple of places and see if that's mentioned.

------------------------------
Rick Marcantonio
Quality Assurance
IBM

Fantastic.  Thanks again!

------------------------------
Scott Terry
------------------------------

Original Message:
Sent: Mon April 19, 2021 09:42 AM
From: Rick Marcantonio
Subject: COMPUTE Syntax Containing Two "Equals" Signs

You're welcome. Just FYI - The help refers to these as "logical expressions." Cf Logical Expressions


------------------------------
Rick Marcantonio
Quality Assurance
IBM
------------------------------


Original Message:
Sent: Mon April 19, 2021 09:03 AM
From: Scott Terry
Subject: COMPUTE Syntax Containing Two "Equals" Signs

Thanks Rick.  Very clear.

------------------------------
Scott Terry


Original Message:
Sent: Tue April 13, 2021 11:59 AM
From: Rick Marcantonio
Subject: COMPUTE Syntax Containing Two "Equals" Signs

It's a boolean evaluation; returns 0 if false and 1 if true. Here 1 if y = z, else 0 (or sysmis if args missing).

data list free /y z.begin data.1 21 1end data.compute x = y = z.list.​

I'll look in the Command Syntax Reference in a couple of places and see if that's mentioned.

------------------------------
Rick Marcantonio
Quality Assurance
IBM