I'm trying to write a formula in Col3 that adds the current value of Col1 with the lagged value of Col2 but I'm running into a pickle trying to figure out how to carry forward the last observation from Col2 when missing data is encountered and to use this value at the first instance of non-missing data. That is, If( !IsMissing( Col1) Col1 + Lag(Col2,1); //create variable that contains current Col2 value; //Else Col1 + previously stored value from Col2; ); I would appreciate any suggestions on how best to accomplish this. Thanks. Row#Col1Col2Col3121 2132315442775.. 6.. 7.. 828992910101111011.. 13.. 1421213152131416114141721516

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Formula to use previous value if not missing, otherwise use value from last occupied cell

terapin

I'm trying to write a formula in Col3 that adds the current value of Col1 with the lagged value of Col2 but I'm running into a pickle trying to figure out how to carry forward the last observation from Col2 when missing data is encountered and to use this value at the first instance of non-missing data. That is,

If( !IsMissing( Col1)
&nbsp;&nbsp;&nbsp;&nbsp; Col1 + Lag(Col2,1);
&nbsp;&nbsp;&nbsp;&nbsp; //create variable that contains current Col2 value;

//Else
&nbsp;&nbsp;&nbsp;&nbsp; Col1 + previously stored value from Col2;

);

I would appreciate any suggestions on how best to accomplish this. Thanks.

Row#	Col1	Col2	Col3
1	2	1
2	1	3	2
3	1	5	4
4	2	7	7
5	.	.
6	.	.
7	.	.
8	2	8	9
9	2	9	10
10	1	11	10
11	.	.
13	.	.
14	2	12	13
15	2	13	14
16	1	14	14
17	2	15	16

Accepted answers

jerry_cooper

I think this formula will give you what you're after:

If( Is Missing( :Column 1 ),
	:Column 1,
	Summation( i = 1, Row(), :Column 1 )
)

Hope this helps.

-Jerry

All comments

txnelson

Here is one version of the formula that works:

If( Row() == 1, lagval = . );&nbsp;
x = Sum( :col 1, lagval );&nbsp;
If( Is Missing( col 2 ) == 0,&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; lagval = :col 2&nbsp;
);
x;

Jeff_Perkinson

I think there's an error in your description that we'll have to clear up before we can give you a precise solution. Your conditional says if that if Col1 is NOT MISSING then add it to the lagged value of Col2, and if Col1 IS MISSING then add that to a previously stored value of Col2.

You can't add a missing Col1 to anything and get anything other than missing.

Having said that, I would build this table out one column at a time. Specifically, I would create a "non-missing Col2" column which had no missing values using the formula:

This formula sets "non-missing Col2" to Col2 when Col2 isn't missing and sets it to the Lag of "non-missing Col2" when Col2 is missing.

You can then use a Lag(non-missing Col2, 1) in your final formula.

I hope that helps.

-Jeff

228103.jmp

terapin

Thanks Jim and Jeff,

I think I made the issue more complicated than it needs to be in my description and table layout and can see how that may have led you to your suggestions.

While I understand your suggestion Jeff about creating a new column that holds the non-missing data I'm hoping to accomplish my work without creating new columns since I'll be using this formula for many different columns. Let me try to be more clear about what I'm trying to accomplish by way of the table below.

I'm trying to create a running sum of Column 1 in Column 2. Without creating any additional columns, I was hoping to create a variable that contains the current running sum value in Column 2 and adds that to the value of Column 1.

My issue is not knowing the best way to create and use a variable that contains the present value for Column 2 so that this value can be "carried" across rows of missing Column 1 data. Column "Result I'm Looking For" shows what I would like the formula in Column 2 to produce. Hopefully this description is a bit more clear about what I'm looking to accomplish.

Untitled 4.jmp

vince_faller

Have we always been able to have a column Formula be self-referential? I never realized I could do this.

jerry_cooper

I think this formula will give you what you're after:

If( Is Missing( :Column 1 ),
	:Column 1,
	Summation( i = 1, Row(), :Column 1 )
)

Hope this helps.

-Jerry

terapin

Thanks everyone for your comments and help.

I think Jerry's suggestion works the best for me and didn't require the use of a local variable which is what I was wanting to use.

markschahl

I run into this problem all of the time and use the solution give by Jerry. I analyze process measurements (temperature, pressure, flow, etc.) that are retrieved from a compressed-data-historian. Every few thousand points, there can be a missing value.

Example below calculates if reactor is running or not based on 3 point moving average of catalyst flow, F.Cat >= 11 (anonymized yes, you get the reference...). If F.Cat is missing, calc uses previous row's value of "Running?".

If(
	Row() < 3, 0,
	Is Missing( :F.Cat ), Lag( :Name( "Running?" ), 1 ),
	(Lag( :F.Cat, 2 ) + Lag( :F.Cat, 1 ) + :F.Cat) / 3 >= 11, 1,
	0
)

cjw0

I think this is exactly what I need as well, but I don't fully understand the script....is it possible to show what this would look like in the formula editor...

thanks so much

cjw0

What I am tyring to do is ask the question....what is the date difference between two different biopsies (column labelled TCMR) for a given patient (pt number in first column) in my database. The biopsies occur at irregular intervales and the outcome of the biopsy is shown in the third column below.

Although I know how to retrieve this information if I simply create a subset of only the rows which contain a biopsy result and then ask for the date difference....what I would likel to do is figure out a way to determine the date difference between any to rows that have a biopsy result while ignoring the empty rows.

@jerry_cooperwrote:
I think this formula will give you what you're after:
If(Is Missing(:Column 1), :Column 1, Summation(i = 1, Row(), :Column 1))
Hope this helps.

-Jerry

Can you help with this. Ideally with a solution that I can see in the formula editor or can paste into it.

Mark_Bailey

You might find the Data Table Tools add-in helpful for such cases.