Often I wish Microsoft had spent the effort and time on a data genie (and a set of powerful formulas) that can automate common data cleanup tasks like extracting duplicates, makings lists unique, find missing items, remove spaces etc. Alas, instead they have provided features like clippy which are intrusive to say the least.
So as part of our second installment of spreadcheats we will learn how to tackle few of the most common data processing tasks:
Getting Unique Items from a List of Cells
There are 3 simple ways to do this:
- Using Advanced Data Filter
- Using countif() and auto filter
- Using formulas as described here
Assuming you have data as shown in the picture aside (and wishing you will have customers like those):
- First add a column to the left of the list. Here we will use formulas to fill numbers based on the uniqueness of the cell next to it.
- Essentially our formula should generate numbers in increasing order as long as the corresponding item is unique and not increase the number otherwise.
- So the formula for order column can be like this:
=IF(COUNTIF(list-upto-that-point, current element)=1,previous-order+1, previous-order)
See the example below:
remember, the first cell order is 1. - See how we are using both absolute and relative references to fetch the counts.
- Now add another column to the right of the list, here we will fetch unique items.
- We will use vlookup() to fetch each of the 12 unique items. The formula goes like this:
=VLOOKUP(running number,$B$4:$C$22,2,FALSE)
You can wrap the vlookup() with if() formula to avoid seeing #value errors.
That is all. Using this method you can extract unique items froma list.
Eliminating Doubles from a List
There are 2 ways in which you can find and remove duplicates(doubles) in excel lists with ease:
- Using countif() and then auto-filter
- Using formulas
The process for finding duplicates using formulas is same as that of finding unique items.
Instead of writing COUNTIF(list-upto-that-point, current element)=1, we now write COUNTIF(list-upto-that-point, current element)=2. Also the first element’s count should be changed to zero.
Once done the list should look like what you see on the side.
Finding Missing Items by comparing one list with another:
Even though this might seem like a different challenge, it is infact same as the above techniques. You need to use countif() to compare first list’s elements with second list. How? that is your home work.
Download and see these formulas in action:
Still having some doubts? Download the excel tutorial – unique & duplicate items and learn by poking around.
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...