From the field to the data file

After conducting the experiment, we collect the data. Data is typically organized in a data file, in the so-called “long format”.

• Each experimental unit is a row in the data file.  
• There are one or more columns that classify the units based on factors (treatments, blocks), and columns with a measurement (response and covariates)  
• In this example, each observed yield (y_ij) is identified by a combination of indexes i =1…7  and  j =1…4  that tag each observation with the treatment and the replication.

The data file organized in this form is the starting point for the analysis.