topic Re: If-function else-clause not recognizing missing values in Discussions

If-function else-clause not recognizing missing values

JesperJohansen — Tue, 10 May 2016 07:12:35 GMT

If I add an If-function to a column, the else-clause does not recognize empty values (see attached sheet). this means that the function:

If( :Column 2 == 1, 1,

2 )

leaves missing values if Column 2 contains missing values. I can fix this by changing the function to:

If( :Column 2 == 1, 1,

Is Missing( :Column 2 ), 2)

If( :Column 2 == 1, 1,

Is Missing( :Column 2 ), 2,

but why is this necessary? Is it a bug or a deliberate "feature"?

Re: If-function else-clause not recognizing missing values

Jeff_Perkinson — Wed, 11 May 2016 20:58:02 GMT

This behavior is intentional and is associated with the propagation of missing values. Your can read a bit about it in the Conditional Functions section of the JMP Scripting Guide.

You should always include a check for missing values in your conditionals.

-Jeff

Re: If-function else-clause not recognizing missing values

Jeff_Perkinson — Wed, 11 May 2016 21:03:10 GMT

If you want to understand why it behaves this way, run this code in your head (and then try it in JMP):

x = .;
If( x < 5, Show( "X is less than five" ),
 x>5, Show( "X is greater than five" ),
 Show("X is equal to five")
);

What did you think it would do?

Re: If-function else-clause not recognizing missing values

JesperJohansen — Fri, 13 May 2016 08:30:05 GMT

I think I came to the same conclusion upon more consideration. That "missing" is not the same as "X is equal to five" in your example. Or whatever else may be placed in the "else" clause.

Thank you