Figure 2
The image contains four line graphs, each representing different types of options: China 50 ETF options, CSI 300 index options, soybean meal futures options, and copper futures options. Each graph plots volatility on the y-axis against moneyness on the x-axis. The graphs compare three interpolation methods: Linear, Cubic, and Spline, each represented by different line styles. The data points are marked by diamonds. The trading dates and expiry dates for each type of option are specified in the note. The graphs show how volatility changes with moneyness for each interpolation method.Linear interpolation, interpolating cubic spline, and 5th-order spline for four kinds of options