doc: Update Row-Column design vignette

vignettes/row_column.Rmd

@@ -19,6 +19,29 @@ knitr::opts_chunk$set(
 
 This vignette shows how to generate a **row-column Design** using both the FielDHub Shiny App and the scripting function `row_column()` from the `FielDHub` package.
 
+## Row-Column Design
+
+It randomly generates a resolvable row-column design (RowColD).The design is 
+optimized in both rows and columns blocking factors. The  randomization can be 
+done across multiple locations.
+
+## Overview
+
+The Row-Column design in FielDHub is built in two stages. The first step 
+constructs the blocking factor `Columns` using Incomplete Block Units 
+from an incomplete block design that sets the number of incomplete blocks as 
+the number of `Columns` in the design, each of which has a dimension 
+equal to the number of `Rows`. Once this design is generated, the 
+`Rows` are used as the `Row` blocking factor that is optimized for 
+A-Efficiency, but levels within the original `Columns` are fixed.
+To optimize the `Rows` while maintaining the current optimized `Columns`, 
+we use a heuristic algorithm that swaps at random treatment positions within 
+a given `Column (Block)` also selected at random. The algorithm begins 
+by calculating the A-Efficiency on the initial design, performs a swap iteration, 
+recalculates the A-Efficiency on the resulting design, and compares it with 
+the previous one to decide whether to keep or discard the new design. This 
+iterative process is repeated, by default, 1000 times.
+
 ## 1. Using the FielDHub Shiny App
 
 To generate a Row-Column Design using the FielDHub app: