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• Configure the Properties of Column 1 in Spreadsheet 1 dialog as shown (Figure 3) with Type set to categorical and Attribute set to factor
  
  

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Creating a categorical sample attribute allows us to group samples. This is useful for designating samples as replicates, as members of an experimental group, or as sharing a phenotype of interest. In this tutorial, we have four different samples from different tissues and different donors, but to illustrate the available statistical analysis options later on, we need to group divide the samples into two groups: muscle (Heart and Muscle) and not muscle (Brain and Liver).  

• Set Attribute name: as Tissueas Tissue
• Rename Group 1 to muscle and Group 2 to not muscle
• Select and drag the samples from the Unassigned panel to the correct group panel (Figure 5)
  
  

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