# Combine Variants Due to fundamental differences between the statistical models employed by different variant detection tools, as well as varying parameter optimizations within tools selected for discrete discovery goals, there can be a large number of unique and common variants identified between each instance of variant detection. In some cases the goal of the study is to provide a list of all possible variants, whereas in other studies the goal is to generate a list of variants with increased confidence of true polymorphic sites. To facilitate both possible goals, *Combine variants* tool generates either the union or intersection of two variants data nodes. This task provides a means to identify common and unique variant calls in samples that have undergone two discrete variant calling tasks. The *Combine variants* task can be invoked from any *Variants* or *Annotated variants* data node, assuming at least discrete variants node(s) exists in the analysis. The task will generate two new variant data nodes and underlying vcf files: one for the union and one for the intersection of the variant data.
To run the task, select a *Variants* data node and then click the **Combine variants** from the task menu. The task dialog will allow you to select a second *Variants* data node to be combined with the first. The selection allows for only one other data node to be used in the task. If there are no other valid variant tasks available within the project, a message stating "No connections to upstream task found" will be displayed.
Currently, this is the only task in Connected Multiomics that requires two *input* data nodes and then generates two *output* data nodes. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://help.connected.illumina.com/icm/analyses/analysis-functionality/task-menu/variant-analysis/combine-variants.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.