Prediction of staple food price at Surabaya city using estimation of fourier series simultaneously

Important indicators of community welfare include the availability and stability of staple food price. Therefore, the government needs to establish economic policies that support one of the goals of the Sustainable Development Goals (SDGs), namely the Poverty Alleviation Goal. Staple food price in Indonesia tend to fluctuate, especially seasonally and at certain times when there is a surge in demand, but it has not been balanced by stock availability. Surabaya, as one of the largest cities in Indonesia, has an important role in economy, not only on a regional scale in East Java but also on a national scale. In this research, secondary data was used in form of data on staple food price in Surabaya from January 2018 to October 2023 with fourteen variables using a simultaneously Fourier series approach. The research results show that the monthly development of staple food price in Surabaya tends to fluctuate, especially the average monthly price of red chilies. The best selected Fourier series estimator is a sin cos basis estimator with y which it has a high value of R2 is 97.046 % and a MAPE value is 9.4179 % can be categorized as very accurate prediction. Then, the prediction results can be used to predict prices of staple food in Surabaya city as reference for making appropriate decision especially for controlling staple food price in the future.