How to...handle Prep errors

***Disclaimer - Prep is rapidly developing so we will try to edit this post to keep up but some 'knowledge' might age but we'll do our best***

Errors in software suck. Who hasn't spent time crying into their keyboard or banging their head against their screen asking the computer gods to find a solution to their problems? Agreed - no one! At Preppin' Data, we are fortunate to have taught a lot of people self-service data prep and Tableau Prep so have a good view on common mistakes people make with the tool. This post will address some of those common issues and pose some potential solutions.

Here's a list of the errors we are going to cover:

  • Parameters
  • Blank profile and data panes
  • Where's my input file? 
  • Why is my input showing as rows rather than columns of data?
  • Whole numbers vs. decimals

Parameters

"...But parameters aren't a thing in Prep" I hear you all cry - correct but you will see this error message a lot:

For those on a small screen the error message reads "Function 'DATEADD' can't accept parameters: (string, integer, string)". 

In this case, parameters are the data fields you are entering into the calculation. The calculation expects a certain data type in these fields and can't accept something that differs. In this specific case, my colleague was using a date in a field that was held as a date. The DATEADD function specifically needs a valid date for the calculation to add the increment on to. 

Therefore, check your data types that you are using in the calculation against what is in the syntax expected (shown in the function help on the right side of the calculated field dialogue box shown in the image. 

Blank profile panes or data panes

This is another common issue I see people find. There are multiple causes for this but we've consistently found a few common causes.

1. Changing a calculation or removing a data field downstream
Here we have created a duplicate NPS field and then removed the original field. Obviously this breaks the flow but we've done it to show the issue that you will get. The red exclamation mark above the step that needs the original NPS shows where the error prevents the flow running but isn't where you would actually fix the flow; that would be in the step before where we have removed the original field.

Use the Changes Pane's in Prep to work your way back through the flow to find where that original field has disappeared from. There's no easy solution here folks but at least this might help you find where to start to work your way backwards. Use the error icon in the top right corner of your flow to read the error but the bottom corner of this dialogue box takes you to where the error is (not the cause of the error as mentioned above).


2. The data source has changed
When you are using any data tool, if the data source changed in anyway - you are likely to get errors; Tableau Prep will be no different. Likely changes to check are:
  1. The data source being used has been moved
  2. The data source has been deleted
  3. The columns used in calculations have been removed
  4. The columns used in calculations have been renamed
All of these will likely result in Prep returning a blank profile pane as no data load will be possible. 

3. Using a whole number in a calculation that will result in a decimal
The following calculation is based on the Cost field being a whole number:

Which causes the following error when you hit apply or save:

To fix this, changing the data type of the Cost field to be a decimal means that Prep can handle the divisions without issue! 

Popular posts from this blog

2023: Week 1 The Data Source Bank

Image
 Created by: Carl Allchin Welcome to a New Year of Preppin' Data. These are weekly exercises to help you learn and develop data preparation skills. We publish the challenges on a Wednesday and share a solution the following Tuesday. You can take the challenges whenever you want and we love to see your solutions. With data preparation, there is never just one way to complete the tasks so sharing your solutions will help others learn too. Share on Twitter, LinkedIn, the Tableau Forums or wherever you want to too. Tag Jenny Martin, Tom Prowse or myself or just use the #PreppinData to share your solutions.  The challenges are designed for learning Tableau Prep but we have a broad community who complete the challenges in R, Python, SQL, DBT, EasyMorph and many other tools. We love seeing people learn new tools so feel free to use whatever tools you want to complete the challenges.  A New Year means we start afresh so January's challenges will be focused on beginners. We will use dif
Read more

2023: Week 2 - International Bank Account Numbers

Image
Challenge By: Jenny Martin For week 2 of our beginner month, Data Source Bank has a requirement to construct International Bank Account Numbers (IBANs), even for Transactions taking place in the UK. We have all the information in separate fields, we just need to put it altogether in the following order: Inputs A list of the transactions, with information about the receiving bank account  A lookup table for the SWIFT Bank Codes  Requirements Input the data In the Transactions table, there is a Sort Code field which contains dashes. We need to remove these so just have a 6 digit string ( hint ) Use the SWIFT Bank Code lookup table to bring in additional information about the SWIFT code and Check Digits of the receiving bank account ( hint ) Add a field for the Country Code ( hint ) Hint: all these transactions take place in the UK so the Country Code should be GB Create the IBAN as above ( hint ) Hint: watch out for trying to combine sting fields with numeric fields - check data types Re
Read more

How to...Handle Free Text

Image
Free isn't always a good thing. In data, Free text is the example to state when proving that statements correct. However, lots of benefit can be gained from understanding data that has been entered in Free Text fields. What do we mean by Free Text? Free Text is the string based data that comes from allowing people to type answers in to systems and forms. The resulting data is normally stored within one column, with one answer per cell. As Free Text means the answer could be anything, this is what you get - absolutely anything. From expletives to slang, the words you will find in the data may be a challenge to interpret but the text is the closest way to collect the voice of your customer / employee. The Free Text field is likely to contain long, rambling sentences that can simply be analysed. If you count these fields, you are likely to have one of each entry each. Therefore, simply counting the entries will not provide anything meaningful to your analysis. The value is in
Read more