Daily DAX : Day 274 PERCENTILE.INC

 The **PERCENTILE.INC** function in Power BI DAX (Data Analysis Expressions) calculates the value at a specified percentile in a dataset, including the minimum and maximum values in the interpolation. It’s used to find a value below which a given percentage of data points fall, making it useful for statistical analysis, such as understanding data distribution or identifying thresholds.

### Syntax

```

PERCENTILE.INC(<column>, <k>)

```

- **`<column>`**: The column containing the numeric values to evaluate.

- **`<k>`**: A number between 0 and 1 (inclusive) representing the percentile (e.g., 0.5 for the 50th percentile or median).

- Returns a single value representing the specified percentile.

### How It Works

- **PERCENTILE.INC** assumes a continuous distribution and interpolates between values if the exact percentile doesn’t correspond to a specific data point.

- It includes both the minimum (0th percentile) and maximum (100th percentile) values in its calculation.

- If `<k>` is 0, it returns the minimum value; if `<k>` is 1, it returns the maximum value.

### Use Case

**Scenario**: A retail company wants to analyze sales amounts to identify performance thresholds.

- **Data**: A table `Sales` with a column `Amount` containing sales values: [100, 200, 300, 400, 500].

- **Goal**: Calculate the 50th percentile (median) and 90th percentile to understand typical and high-performing sales.

**DAX Example**:

```dax

MedianSales = PERCENTILE.INC(Sales[Amount], 0.5)

```

- Result: 300 (the median, as it’s the middle value in the ordered list).

```dax

Top10PercentSales = PERCENTILE.INC(Sales[Amount], 0.9)

```

- Result: Interpolates between 400 and 500, yielding approximately 460 (since 90th percentile lies between the 4th and 5th values in a 5-value dataset).

### Practical Applications

1. **Performance Analysis**: Identify benchmarks, like the sales amount below which 80% of transactions fall.

2. **Outlier Detection**: Use high percentiles (e.g., 95th) to flag unusually large values.

3. **Financial Reporting**: Calculate thresholds for bonuses or risk assessment (e.g., 75th percentile of expenses).

4. **Customer Segmentation**: Determine spending thresholds to segment customers (e.g., top 10% spenders).

### Notes

- **PERCENTILE.INC** vs. **PERCENTILE.EXC**: Use `PERCENTILE.INC` for inclusive interpolation (includes min/max); use `PERCENTILE.EXC` for exclusive interpolation (excludes min/max, requires larger datasets).

- Ensure `<column>` contains numeric values, or use a filter to avoid errors.

- If the dataset is small, interpolation may lead to less precise results.

For more complex scenarios, combine with filters or other DAX functions like `FILTER` to focus on specific data subsets.