“…Non-parametric regression is used when the assumption of the relationship between the predictor and the response is unknown, so we must estimate its function. Some estimators that have been developed include spline truncated (Aprilia, Islamiyati and Anisa, 2019), spline smoothing (Lestari, Budiantara and Chamidah, 2019), spline penalized (Islamiyati, Fatmawati and Chamidah, 2019), local polynomial (Chamidah, Gusti, Tjahjono and Lestari, 2019), Kernel (Chamidah and Saifuddin, 2013), Fourier series (Mardianto, Tjahjono and Rifada, 2020), and Gaussian process (Saegusa, 2020) , and spline principal component analysis (Islamiyati, Kalondeng, Sunusi, Zakir and Amir, 2022). For this article, we use spline truncated to estimate multi-variable non-parametric regression functions.…”