Forum Discussion
Generating a 2D array from sumifs on the columns of another 2D array
James_Buist As a variant, here's a couple of SUMIFS options:
=LET( arr, LAMBDA(n, CHOOSE(n, K10#, SEQUENCE(, COLUMNS(M2#)))), MAP(arr({1}), arr({2}), LAMBDA(r,c, SUMIFS(INDEX(M2#,, c), K2#, r))) )-OR-
=DROP(REDUCE(0, SEQUENCE(COLUMNS(M2#)), LAMBDA(p,c, HSTACK(p, SUMIFS(INDEX(M2#,, c), K2#, K10#)))),, 1)The latter should be more efficient because there are fewer iterations, but you probably won't notice a difference on a relatively small dataset.
Having said that, I'd be more interested to see how the actual data source is organized. Obviously, cells K2 and M2 contain formulas that reference another dataset, because you're using the spilled range operator (#). If the data source was arranged vertically in a table with columns for "Division", "Month" and "Amount", you could easily summarize the data using a single SUMIFS formula or a pivot table.
Please see the attached example file, if needed...
James_Buist As a variant, here's a couple of SUMIFS options:
=LET(
arr, LAMBDA(n, CHOOSE(n, K10#, SEQUENCE(, COLUMNS(M2#)))),
MAP(arr({1}), arr({2}), LAMBDA(r,c, SUMIFS(INDEX(M2#,, c), K2#, r)))
)
-OR-
=DROP(REDUCE(0, SEQUENCE(COLUMNS(M2#)), LAMBDA(p,c, HSTACK(p, SUMIFS(INDEX(M2#,, c), K2#, K10#)))),, 1)
The latter should be more efficient because there are fewer iterations, but you probably won't notice a difference on a relatively small dataset.
Having said that, I'd be more interested to see how the actual data source is organized. Obviously, cells K2 and M2 contain formulas that reference another dataset, because you're using the spilled range operator (#). If the data source was arranged vertically in a table with columns for "Division", "Month" and "Amount", you could easily summarize the data using a single SUMIFS formula or a pivot table.
Please see the attached example file, if needed...
- I tested the three options with 5000 rows and 180 columns. The MAKEARRAY solution took around 5 seconds to calculate / process. ie clicking in the cell with a SPILL error to having a display of the results was around 5s and similar time for a full alt ctrl F9 calc. In addition, it would need additional handling for non matches ie if a division has no costs as these result in a calc error
On the other hand, it is impossible to tell what the performance difference is between REDUCE and the LET with MAP as they are both lightning fast. Clicking in the cell with a spill error and tabbing out results in immediate display of results and with a full calc (I'm using manual calc) the calc flashes up then goes. Think I'd need to test with 100K rows to get a real gauge.
So I will stick with the LET & MAP which remain the nest solutions. either.James_Buist MMULT is also a possibility:
=MMULT(--(K10# = TOROW(K2#)), M2#)This is both the shortest and most efficient method for your layout. However, since you "need the simplest possible solution that others later may understand", it may or may not be the way to go, as it's not the easiest method to understand and/or modified to meet new criteria.
Regarding the MAP / CHOOSE method, this was offered as a relatively efficient alternative to the MAKEARRAY / INDEX method, but not necessarily the most efficient method overall. As with most situations in Excel, there are many different ways to get the job done. Ultimately, it comes down to the method you prefer, while maintaining efficiency relative to the size of the dataset you're working with.
To demonstrate the difference in calculation speed between MAP / CHOOSE and MAKEARRAY / INDEX, try the following comparison test:
=LET( arr, LAMBDA(n, CHOOSE(n, SEQUENCE(1000,,,2), SEQUENCE(,1000,,5))), MAP(arr({1}), arr({2}), LAMBDA(r,c, r+c)) ) \\compared to: =LET( rs, SEQUENCE(1000,,,2), cs, SEQUENCE(,1000,,5), MAKEARRAY(1000, 1000, LAMBDA(r,c, INDEX(rs,r)+INDEX(cs,c))) )On my system, MAP took only 1 second to return the results, whereas MAKEARRAY took almost 30.
(Obviously =SEQUENCE(1000,,,2)+SEQUENCE(,1000,,5) is all that's needed here, but that would defeat the purpose of the test, lol.)
Cheers!
Many thanks for these. Brilliant
Firstly, the dataset is just a small subset. Should have mentioned that in the post. Actually there will be up to 200 columns and 10 rows so around 2K cells in all, reading off another dataset of up to 200 columns and maybe 100 rows. The main data set to sumif by column.
I actually prefer the first answer just because I do find LET really good and easy to break down what is happening – I change the outputs to subparts to analyse. Also I already tried this solution with MAP but failed so was sort of on the right track with one approach. Love the clever use of Choose as a function within.
I like the REDUCE solution too but I haven’t totally got my head around the more complex Scan and Reduce use cases – but need to. I had also tried a solution with REDUCE but couldn’t get it to work. But I think it is harder to break down and analyse than the LET & MAP option and I need other third parties to be able to follow this. Thus I feel that explaining the Let solution is simpler. But I will also try with a much larger dataset and see what performance differences there are.
Finally, thanks also for the SUMIFS solution. I had also tried expanding out the array as an option but couldn’t figure out that either. The use of TOCOL with the If({1}) is really cool as it coerces the small array into the larger one. I couldn’t figure out how to do this. Again, I could wrap this in a LET function to do it all in one though would have to use SUMPRODUCT instead of SUMIFS as it would be reading from a DA rather than a range
Sorted me out and was also very educational
Many thanks
