Question is regarding how to get top x% of records according to their ratings.
For example I have a table with a few columns, one of which is rating:
rating smallint
value of rating is always positive.
My goal is to select top x% of entries according to their rating.
For example, for top 20%, if set of selected rows contains ratings like:
1,3,4,4,5,2,7,10,9
Then top 20% would be records with range from 8 to 10 → records with rating 9 and 10.
I implemented it in Django but it takes 2 calls to DB and I believe it can be easily achieved via SQL in PostgreSQL by just one call.
Any ideas how to implement it?
Considering that the max rating available in the column is your base for max calculation.
Try this workaround:
select * from sample where rating >=(select max(rating)-max(rating)*20/100 from sample)
Demo on fiddle
Related
I'm not sure if you can quick question someone can provide me with an answer for.
I am trying to add a total number of records to the title of a sheet, however every calculated field I do returns "1" as they must be just counting one row not all the rows.
Tried:
TOTAL(SUM([Number of Records]))
COUNT([Number of Records])
COUNTD([Number of Records])
I would like the title to say "Incidents Active over 7 days Total 12" (or whatever the number of records in the sheet are)
Put a calculated field that simply calls Size() on the detail shelf.
Click on that field and then Edit the Table calc to define the partitioning and addressing (aka compute using) This is the trickiest part. From your screen shot, it looks like you'd want to choose Specific Dimensions, and then set At the Level to Number. You may need to experiment or RTFM.
Insert Size() into your title
To understand how this works, especially the tricky step 2, read the on line help about Table Calc, and check out some of the videos and training materials on table calcs from the Tableau Conference. Last year's are available at http://tc19.tableau.com
I have data split between two different tables, at different levels of detail. The first table has transaction data that, in the fomrat:
category item spend
a 1 10
a 2 5
a 3 10
b 1 15
b 2 10
The second table is a budget by category in the format
category limit
a 40
b 30
I want to show three BANs, Total Spend, Total Limit, and Total Limit - Spend, and be able to filter by category across the related data source (transaction is related to budget table by category). However, I can't seem to get the filter / relationship right. That is, if I use category as a filter from the transaction table and set it to filter all using related data source, it doesn't filter the Total Limit amount. Using 2018.1, fyi.
Although you have data split across 2 tables they can be joined using the category field and available as a single data source. You would be then be able to use category as a quick filter.
Thanks in advance for any advice you can offer! I'm building a Tableau dashboard to explore housing affordability and school quality in different neighborhoods in my area. A user will select their occupation and see a graph of neighborhoods plotted based on school quality and housing affordability. To explore housing affordability, I'm using county level assessor data with the valuation of every property matched to neighborhoods.
The goal is to display the percentage of homes in an area that are affordable given the median occupational wages for the job a user selected. Right now, I'm trying to use a calculated field with COUNT([Parcels]<[Occupation])/COUNT([Parcels]), but I need to find a way to count the number of properties in each specific neighborhood below the cut off value.
Does anyone know of a way to count elements of a particular group in this way in Tableau?
I'm on a Mac, using Tableau Desktop, and doing the back end analysis work in R. Thank you!
You seem to misunderstand what the function COUNT() does. You are certainly not alone. Count() behaves in Tableau almost identically to how it does with SQL.
Count([some field]) returns the number of data rows where the value for [some field] is not null. It does not not return the number of rows where [some field] evaluates to true, or a positive number, or anything else.
If [some field] always has a non-null value, then Count([some field]) is the same as SUM([Number of Records]). If [some field] is always null, then Count([some field]) is zero. Count() is not like Excel's CountIf function.
If you want to count data rows that meet a condition, you could try COUNT(if [condition] then 1 end) Since the missing ELSE case defaults to null values, that expression will count rows where [condition] is true.
So one way to get the percentage of affordable homes is count(if [affordable] then 1 end) / count(1) assumes each Data row represents a home. Then format your field to display as a percentage. Another option is to learn to use quick table calcs
If you want to display the number of rows in a given visualized table you could also use SIZE()
Source, official docs:
https://help.tableau.com/current/pro/desktop/en-us/functions_functions_tablecalculation.htm#size
I've got some data that I'd like to display both the averages and the count for.
For instance, there are 50 People taking a survey. Their names are saved in a Dimension "Raters". They are taste testing several products. These products are saved in a Dimension "Products"
They answer 4 questions. Taste, Texture, Appearance, Uniqueness, all saved in Dimension "Question"
The actual ratings are saved in "Ratings". This is a measure.
I can very easily make a table with Raters on the Rows, Question on the Columns, AVG(Ratings) in the text.
This shows me the average score for each question the rater answered.
It looks like this:
Rater-----Taste-----Texture-----Appearance-----Uniqueness
Joe---------2.2---------4.3--------------3.7-----------------2.4
Bob--------3.0----------1.2-------------3.4-----------------4.4
Sally-------4.5----------3.3-------------4.5-----------------3.2
Jessica---5.0----------3.0-------------2.0-----------------1.0
So far, so good.
Jessica's results look suspiciously integerish. When I look at the background data, I see that she only answered for 1 product.
I'd like to be able to add a column to the right of uniqueness which is the count of all product responses for that person.
I've played with this quite a bit, and I'm not sure that it is possible. Maybe with LOD?
I'd also like to filter the table, so that only "tough" raters are shown. Criteria for this is: Their average response for at least two criteria should be below 3.0. That would include Joe and Jessica.
When I try to do counts based on averages, I run into the "cannot aggregate an aggregate rule".
Is there a way around this? It would be trivial to do in excel with another column, a countif, and a filter.
Thanks,
Chris
Part 1:
You should be able to create a calculated field(Analysis->Calculated Field) and name it something like "Number of Records". In the query box just set it to 1 and select "Okay".
This new field will be selectable in the measures. Drag it into your table in the columns area and it should add a count next to your averages.
Part2:
In your measure values box you should be able to right click you measures. This will bring up a list of options including "Filter". Select this option.
On the SUM(Number of Records) set it to "At Least" = 2. Then right click on the AVG(Ratings) measure and set it to "At Most" = 3
Put Products on the Rows shelf.
Then right click on that Products field on the Rows shelf and change ITT from a dimension to a measure. Be sure to choose Count Distinct for the aggregation.
Finally, right click on the field again and change it from continuous to discrete.
This shows how many different products each person reviewed, no matter how many characteristics they rated. If you want the number of ratings, use count instead of count distinct. Or just Sum(number of records), again set to discrete
I am quite new to Tableau, so have patience with me :)
I have two tables,
Table one (T1) contains all my data with the first row being Year-Week, like 2014-01, 2014-02, and so on. Quick question regarding this, how do I make Tableau consider this as a date, and not as string?
T1 contains a lot of data that looks like this:
YearWeek Spend TV Movies
2014-01 5000 42 12
2014-02 4800 41 32
2014-03 2000 24 14
....
2015-24 7000 45 65
I have another table (T2) that contains information regarding some values I want to multiply with the T1 columns, T2 looks like:
NAME TV Movies
Weight 2 5
Response 6 3
Ad 7 2
Version 1 0
I want to create a calculated field (TVNEW) that takes the values from T1 of TV, and adds Response(TV) to it, and times it with the weight(TV),
So something like this:
(T1[TV]+T2[TV[Response]])*T2[TV[Weight]]
This looks like this for the rows:
(42+6)*2
(41+6)*2
(24+6)*2
...
(45+6)*2
So the calculation should take a specific value from T2, and do the calculation for each value in T1[TV]
Thanks in advance
The easy answer to your question will be: No, not natively.
What you want to do sounds like accessing a 2 dimensional array and that's not really the intention of Tableau. Additionally you have 2 completely independent tables without a common attribute to JOIN on. Tableau is just not meant to work that way.
I cannot think of a way to dynamically extract that value (I assume your example is just that, an example; and in your case you don't just use two values in the calculation, otherwise you could create 2 parameters that you can use in your calculated fields)
When I look at your tables it looks like you could transpose and join them that they ideally look like this: (Edit: Comment says transposing is not an option)
Medium Value YearWeek Spend
Movies 12 2014-01 5,000
Movies 32 2014-02 4,000
Movies 14 2014-03 2,000
Movies 65 2015-24 7,000
TV 42 2014-01 5,000
TV 41 2014-02 4,000
TV 24 2014-03 2,000
TV 45 2015-24 7,000
and
Medium Weight Response Ad Version
TV 2 6 7 1
Movies 5 3 2 0
Depending on the systems you work with you could already put it in one CSV or table so you wouldn't have to do a JOIN in Tableau.
Now you can create the first table natively in Tableau (from Version 9.0 onwards), if you open your data source, in the Data Source Preview choose the columns TV and Movies, click on the small triangle and then on Pivot. (At this point you can also choose the YearWeek column click on the triangle and Split to create a seperate field for Year and Week. You won't be able to assign the type date to it put that shouldn't give you any disadvantages.)
For the second table I can think of two possibilities:
you have access to a tool that can transpose your table (Excel can do that see: Convert matrix to 3-column table ('reverse pivot', 'unpivot', 'flatten', 'normalize') Once you have done that you can open it in Tableau and join the two tables on Medium
You could create calculated fields depending on the medium:
Field: Weight
CASE [Medium]
WHEN 'TV' THEN 2
WHEN 'Movies' THEN 5
END
And accordingly for Response, Ad and Version
Obviously that is only reasonable if you really just need a handfull of values.
Once this is done it's only a matter of creating a calculated field with
([Value]+[Response])*[Weight]
And this will calculate all the values for your table