Google Sheets – Create Sparkline for Delta Between Columns

No formulae are needed. Just select the range, Insert, Chart..., select Histogram, Insert. For the sample as above a bin size of 2 will be automatically selected but this can be changed to 1 by right-clicking the chart area, Advanced edit..., entering 1 for Bucket size and Update.

Result should look something like:

The name and concept of this function comes from Kronecker delta, and it is used for the same reason as it's used in mathematics and engineering: to include equality conditions into algebraic expressions. Excel had this function for a while; the old version of Google Sheets did not, which was noticed. So, if nothing else, better compatibility with Excel is a reason enough to add this function.

As an example, it can be used for things like "the number of places where the numbers in columns A and B agree":

=sum(arrayformula(delta(A1:A,B1:B)))

Of course there are other ways to do the same, like countif: the point of delta is that one could have it in a complex algebraic expression.

The above doesn't quite work with eq: the formula =sum(arrayformula(eq(A1:A,B1:B))) throws an error. One can get around it with =sum(arrayformula(1*eq(A1:A,B1:B))) by converting boolean to integer.