Taking difference of two columns when one column is blank

[afleiderman1]

I got the following question

My rows are customer name.

My column are week dates

my measure are previous,current, and differnece sales.

diff=current-previous 

example

                     January 14                                                      January 21                                January 28      

                  Previous     Current         diff              previous current       diff               previous current    diff

James         blank       20               20                   20           10                 -10          10            30            20

Basically I only have dates up to January 14. So the week previous to January 14 will be blank. What I want is for the diff column for the Janaury 14 to also be blank because I do not have that data. I want my other columns to remain the same. 

[v-yangliu-msft · Accepted solution]

Hi  @afleiderman1 ,

Here are the steps you can follow：

1. Create measure.

current =
 SUMX(
     FILTER(ALL('Table'),
     'Table'[Customer name]=MAX('Table'[Customer name])&&'Table'[week]=MAX('Table'[week])),[Value])

Previous =
 SUMX(
     FILTER(ALL('Table'),
     'Table'[Customer name]=MAX('Table'[Customer name])&&'Table'[week]=MAX('Table'[week])-1),[Value])

diff =
IF(
    [Previous] = BLANK(),BLANK(),
[current] - [Previous])

2. Result:

Best Regards,

Liu Yang

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly

[afleiderman1]

I think I can use isblank here