Condition error

[#1]

hello

I'm trying to do a delta check between neighboring cells value on the same column.

For( i = 1, i <= N Row( dtB ), i++,
    If(
        i == 1,
            If( Abs( :Delta[i] - :Delta[i + 1] ) <= 0.1,
                dtB:Check[i] = "Pass",
                dtB:Check[i] = "Fail"
            ),
        i == N Row( dtB ),
            If( Abs( :Delta[i] - :Delta[i - 1] ) <= 0.1,
                dtB:Check[i] = "Pass",
                dtB:Check[i] = "Fail"
            ),
        If( Abs( :Delta[i] - :Delta[i + 1] ) <= 0.1 | Abs( :Delta[i] - :Delta[i - 1] ) <= 0.1,
            dtB:Check[i] = "Pass",
            dtB:Check[i] = "Fail"
        )
    )
);

i get this result

but line 5 should not fail
when I check it thru the log it seems like a bug or I'm missing something
appreciate your inputs

i
/*:

5
//:*/
:Delta[i]
/*:

0.3
//:*/
:Delta[i+1]
/*:

0.4
//:*/
abs(:Delta[i] - :Delta[i+1])
/*:

0.1
//:*/
abs(:Delta[i] - :Delta[i+1]) <= 0.1
/*:

0

[#2]

If I understand what you are trying to do, then this simplified version might work:

For Each Row(
	dtB:Check = If( Abs( :Delta - Lag(:Delta) ) <= 0.1, "Pass", "Fail" );
);

[#3]

I like to check the cell value matching (up to 0.1) from both "sides" n+1 and n-1 in this column. 1st and last rows on one side.
thank you 

[#4]

abs(-0.4 - 0.3 ) = 0.7

abs(-0.4) - abs(0.3) = 0.1

[#5]

sorry, didn't get it.

i = 5;
:Delta[i] = 0.3;
:Delta[i+1] = 0.4;
abs(:Delta[i] - :Delta[i+1]) = 0.1;
// but 
abs(:Delta[i] - :Delta[i+1]) <= 0.1 // give me 0

 why is that? also == give me 0, >= give 1.

[#6 · Accepted solution]

I confirm this error with the follow code (view results in Log):

/* Abs( 0.4 - 0.3) == 0.1; returns 0 or false */

y = 0.1; x1 = 0.4; x2 = 0.3; diff = x1 - x2;
Show( y, x1, x2, diff, diff == 0.1 );

[#7]

One more thing to check would be the difference between diff and 0.1

diff - 0.1 = 2.77555756156289e-17;

so floating number accuracy "problem"?

Round(diff, 1) == Round(0.1, 1) = 1;

[#8 · Accepted solution]

That's your basic floating point roundoff error.  Add an epsilon and it works:

Deltai = 0.3;
Deltai1 = 0.4;
epsilon = .000000001;
print(abs(Deltai - Deltai1));	// = 0.1;
print(abs(Deltai - Deltai1) <= 0.1);
print(abs(Deltai - Deltai1) <= 0.1 + epsilon);

From the log:

0.1
0
1

[#9]

JMP Development confirmed that this is simply a finite precision numerical problem. Users are disturbed by floating point numbers that do not follow the math (e.g., subtraction). JMP tries to present the result as it is expected, but not the actual result in cases like yours (i.e., 0.4 - 0.3). They suggested also using this approach if you want a better view of the actual result:

Format( 0.1, "Fixed Dec", 20, 22 );
Format( 0.4-0.3, "Fixed Dec", 20, 22 );

[#10]

The issue is that the difference from minus .4 to a positive .3 is .7.  The Absolute of the values are taken after the calculation!