> For the complete documentation index, see [llms.txt](https://docs.coupler.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.coupler.io/troubleshooting/data-sets-preview-troubleshooting-guide.md).

# Data sets (Preview) Troubleshooting Guide

### You're trying to use a string as a boolean

You may encounter the following error when using a formula in your data flow:

> You're trying to use a string as a boolean. Consider using a boolean expression or casting the value to boolean.

<figure><img src="https://2487187314-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FCgnmco7kCnvytNIN8YdT%2Fuploads%2FCFffcUKb0xnGBpgvoTS6%2Fimage.png?alt=media&amp;token=390da162-6128-4a85-bd5d-1b512357ac79" alt=""><figcaption></figcaption></figure>

This error occurs when a formula expects a **boolean** value (`TRUE` or `FALSE`), but receives a **string** instead.

For example, logical functions and operators such as `IF`, `!`, `AND()`,  `OR()` , etc. expect boolean values as their arguments. If the column you're using contains a string instead of actual boolean values, the formula may return this error.

**How to fix it**

1. Open the affected data flow and go to the Data sets section.
2. Check the formulas you've added. Formulas can be configured at both the ***data source and data set levels***, so make sure to review formulas in both places.
3. Look for logical functions or operators, such as:
   * `IF`
   * `!`
   * `AND()`
   * `OR()`
   * Other [logical functions](https://docs.coupler.io/functionality/preview-data/adding-formula-based-custom-columns#logical-functions)
4. Check the data type of the column used in the formula. Make sure it contains a boolean value rather than a string.
5. If the value is stored as a string, update your formula to use a boolean expression or convert the value to a boolean before using it in a logical function.\
   **Example**: One common case is when you have a formula like\
   `IF({{column}},1,0)` and the `{{column}}` is a string. This can trigger the error, so instead, you can specify `IF(LENGTH({{column}})>0,1,0)`


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