> For the complete documentation index, see [llms.txt](https://docs.finngen.fi/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.finngen.fi/working-in-the-sandbox/which-tools-are-available/atlas/detailed-guide/how-to-define-a-cohort-in-atlas/how-to-define-a-simple-icd-case-control-cohort-in-atlas/define-a-simple-icd-control-cohort-in-atlas.md).

# Define a simple ICD control cohort in Atlas

This example shows how to build a simple "all who are not cases" control cohort using the Finnish-specific H81 ICD10fi codes.

### Step 1: Clone the case cohort

* Click the **Cohort Definitions** on the left menu and open your case cohort (e.g. Test\_Cohort\_Cases\_MN):

<figure><img src="https://3072695768-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhYL0UTLjqsuIdK0SSO%2Fuploads%2Fgit-blob-fe5e241bee82153c2d7e1401a0581852f5dc1453%2Fimage%20(393).png?alt=media" alt=""><figcaption></figcaption></figure>

* **Clone** the cohort by clicking the copy button <img src="https://3072695768-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhYL0UTLjqsuIdK0SSO%2Fuploads%2Fgit-blob-49979acdec3d30d504b1864d5bf576cf1af80d75%2Fimage%20(388).png?alt=media" alt="" data-size="line">
* The name of the cloned cohort is "COPY OF ...". **Rename** the cohort as the controls cohort (e.g. Test\_Cohort\_Controls\_MN)
* **Save** the cohort by clicking the save button <img src="https://3072695768-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhYL0UTLjqsuIdK0SSO%2Fuploads%2Fgit-blob-8a010ae33fa5327a89cbf047de77d491ba768403%2FScreenshot%202023-05-28%20at%2017.56.06.png?alt=media" alt="" data-size="line">

### Step 2: Change the Inclusion Criteria

* **Open** the **Inclusion Criteria** by clicking its name (e.g. TestPhenotypeCases). This will open the inclusion criteria specified for the cases cohort.

<figure><img src="https://3072695768-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhYL0UTLjqsuIdK0SSO%2Fuploads%2Fgit-blob-cf5c813080281de65d2afa188eb53348d38a5f01%2Fimage%20(236).png?alt=media" alt=""><figcaption></figcaption></figure>

* **Rename the Inclusion Criteria** (e.g. TestPhenotypeControls).
* **Change the Inclusion Criteria** from **"at least 1**” to "**with exactly 0**” and leave all other settings unchanged:

<figure><img src="https://3072695768-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhYL0UTLjqsuIdK0SSO%2Fuploads%2Fgit-blob-c598c8f8f1719a3f8f112e2e6ecec6de9122331b%2Fimage%20(193).png?alt=media" alt=""><figcaption></figcaption></figure>

* **Save** the cohort by clicking the save button <img src="https://3072695768-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhYL0UTLjqsuIdK0SSO%2Fuploads%2Fgit-blob-8a010ae33fa5327a89cbf047de77d491ba768403%2FScreenshot%202023-05-28%20at%2017.56.06.png?alt=media" alt="" data-size="line">

### Step 3: Generate the control cohort

* Open the **Generation** tab and generate the cohort by clicking the **Generate** button next to the same FinnGen data release you used to create the case cohort (FinnGen CDM R11 in the screenshot below). The cohort generation will take a few minutes and the speed is not dependent on the size of the sandbox IVM.

<figure><img src="https://3072695768-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhYL0UTLjqsuIdK0SSO%2Fuploads%2Fgit-blob-2578349fc0291bc0a831a2704f2ad3f7d2a2a7fd%2Fimage%20(775).png?alt=media" alt=""><figcaption></figcaption></figure>

The control cohort is now ready. This cohort can (and should) be [explored within Atlas](/working-in-the-sandbox/which-tools-are-available/atlas/detailed-guide/cohort-characterizations-in-atlas.md) and used in [Cohort Operations](/working-in-the-sandbox/which-tools-are-available/cohort-operations-tool-co.md) and [Trajectory Visualization tool](/working-in-the-sandbox/which-tools-are-available/trajectory-visualization-tool-tvt.md). The cohort may also be [exported from Atlas](/working-in-the-sandbox/which-tools-are-available/atlas/detailed-guide/how-to-define-a-cohort-in-atlas/how-do-you-export-finngen-ids-for-an-analysis-cohort.md) for further analyses like those described in the [General Workflows for the most common analyses](/working-in-the-sandbox/general-workflows-for-the-most-common-analyses.md).