update README.

Author: smeghead

README.md

@@ -186,18 +186,69 @@ VariableHardUsage is an index used to evaluate the frequency of use and scope of
 
 ### Calculation Procedure
 
-1. Obtain the line numbers of the references to the same variable:.
+This tool calculates the **Variable Hard Usage** score for each **scope** (i.e., a function or method) based on how local variables are used. The calculation consists of the following steps:
 
-  * For each variable used in the function, retrieve all line numbers where the variable is referenced.
+---
 
-2. Calculate deviation based on first occurrence.
+#### 1. Extract local variables in a scope
 
-  * For each reference, computes the difference between the line number and the line number of the first occurrence of the variable.
+For each scope $S$, extract all local variables:
 
-3. Applying coefficients by assignment.
-  * When a variable is assigned, the difference is multiplied by a coefficient (2 by default). This is to account for the effect of the assignment on the frequency of use of the variable.
-  * Calculation of VariableHardUsage:.
-  * The VariableHardUsage is obtained by summing all these deviation values.
+$$
+V = {v_1, v_2, ..., v_m}
+$$
+
+---
+
+#### 2. For each variable $v_j$, identify lines where it is referenced
+
+Let the variable $v_j$ be referenced at line numbers:
+
+$$
+L^{(j)} = {l^{(j)}_1, l^{(j)}_2, ..., l^{(j)}_{n_j}} \quad \text{(sorted in ascending order)}
+$$
+
+---
+
+#### 3. Assign weights to each reference
+
+Each reference line $l^{(j)}_i$ is assigned a weight $w^{(j)}_i$ depending on whether it is a simple read or an assignment:
+
+- If the reference is **an assignment (update)**:  
+  $$
+  w^{(j)}_i = \alpha \quad (\text{default: } \alpha = 2)
+  $$
+
+- If the reference is **a read-only access**:  
+  $$
+  w^{(j)}_i = 1
+  $$
+
+---
+
+#### 4. Calculate Variable Hard Usage for each variable
+
+Let $l^{(j)}_\text{base} = l^{(j)}_1$, the first line where $v_j$ appears.
+
+Then, the hard usage score for $v_j$ is calculated as:
+
+$$
+H(v_j) = \sum_{i=1}^{n_j} w^{(j)}_i \cdot |l^{(j)}_i - l^{(j)}_\text{base}|
+$$
+
+This measures how widely and intensely the variable is used, with updates having a stronger impact.
+
+---
+
+#### 5. Sum all variable scores to get the score for the scope
+
+The total **Variable Hard Usage** for the scope $S$ is:
+
+$$
+H(S) = \sum_{j=1}^{m} H(v_j) = \sum_{j=1}^{m} \sum_{i=1}^{n_j} w^{(j)}_i \cdot |l^{(j)}_i - l^{(j)}_\text{base}|
+$$
+
+A larger value of $H(S)$ indicates that variables in the scope are heavily and broadly used, which may reduce code readability and maintainability.
 
 ### Example