Last night I got an email from Joshua, one of our readers with the subject – Hard Excel problem. Hard?!?, at this stage of summer, the hard problems seem to be (in no particular order),
- Lack of good quality mangoes to eat
- Intense heat and humidity
- Lack of good quality mangoes to eat
Yes, I like mangoes.
Any how, back to Joshua’s email, So I got curious and read it. He is facing an interestingproblem.
I have a very difficult inquiry I am hoping you might be able to solve…
Is there a formula (i.e., without using VBA) that will look at another columns values and provide a new sequential number (i.e., reordered) when the value changes; however, keep the same sequential number for the duplicates?
Below is a table with two columns. […] I now need to rank order those cluster groups. Since cluster 12 appears first it would get a value of ‘1’ and all of the cluster 12’s should now be a ‘1’. Since cluster 4 appears next it would get a rank of 2, etc…
Well, it is an interesting problem for sure. But hard problem, it isn’t. For really hard problems, refer to my list above.
So how to generate the sequence numbers?
Logic: If a value is already listed, we fetch corresponding sequence number. Else, we generate a new sequence number.
Implementation: Simple, we use VLOOKUP.
Assuming the cluster values are in column B, from B4 onwards, in C4, write
=IFERROR(VLOOKUP(B4,$B$3:C3,2,FALSE), SUM(MAX($C$3:C3),1))
Let’s examine the formula.
VLOOKUP(B4,$B$3:C3,2,FALSE) portion: This one looks value in column B and tries to find corresponding sequence value in column C.
SUM(MAX($C$3:C3),1) portion: Gives us next sequence number
IFERROR(VLOOKUP(…), SUM(…)) portion: This does the magic of choosing either existing sequence number or generating a new one.
For more, read about VLOOKUP and IFERROR formulas.
Sequence number generation – Example spreadsheet
Play with the sequence number generation spreadsheet embedded below or Click here to grab a copy of the file.
How would you generate the sequence numbers?
Its your turn to take a crack at the hard problem. How would you solve it? Go ahead and share your answers in the comments.
More hard problems – solved:
Hard problems are not new at Chandoo.org. We take lob vlookups and sumproducts regularly to crack them. Here are few examples:
8 Responses to “Pivot Tables from large data-sets – 5 examples”
Do you have links to any sites that can provide free, large, test data sets. Both large in diversity and large in total number of rows.
Good question Ron. I suggest checking out kaggle.com, data.world or create your own with randbetween(). You can also get a complex business data-set from Microsoft Power BI website. It is contoso retail data.
Hi Chandoo,
I work with large data sets all the time (80-200MB files with 100Ks of rows and 20-40 columns) and I've taken a few steps to reduce the size (20-60MB) so they can better shared and work more quickly. These steps include: creating custom calculations in the pivot instead of having additional data columns, deleting the data tab and saving as an xlsb. I've even tried indexmatch instead of vlookup--although I'm not sure that saved much. Are there any other tricks to further reduce the file size? thanks, Steve
Hi Steve,
Good tips on how to reduce the file size and / or process time. Another thing I would definitely try is to use Data Model to load the data rather than keep it in the file. You would be,
1. connect to source data file thru Power Query
2. filter away any columns / rows that are not needed
3. load the data to model
4. make pivots from it
This would reduce the file size while providing all the answers you need.
Give it a try. See this video for some help - https://www.youtube.com/watch?v=5u7bpysO3FQ
Normally when Excel processes data it utilizes all four cores on a processor. Is it true that Excel reduces to only using two cores When calculating tables? Same issue if there were two cores present, it would reduce to one in a table?
I ask because, I have personally noticed when i use tables the data is much slower than if I would have filtered it. I like tables for obvious reasons when working with datasets. Is this true.
John:
I don't know if it is true that Excel Table processing only uses 2 threads/cores, but it is entirely possible. The program has to be enabled to handle multiple parallel threads. Excel Lists/Tables were added long ago, at a time when 2 processes was a reasonable upper limit. And, it could be that there simply is no way to program table processing to use more than 2 threads at a time...
When I've got a large data set, I will set my Excel priority to High thru Task Manager to allow it to use more available processing. Never use RealTime priority or you're completely locked up until Excel finishes.
That is a good tip Jen...