Abstract: A graph display control apparatus includes a processor. The processor operations including: storing a function equation in a memory; displaying a graph corresponding to the stored function equation on a coordinate system of a display; designating a plurality of points on the displayed graph in response to user's operations; obtaining a slope value of a tangent to the displayed graph at each coordinate corresponding to each of the plurality of designated points; plotting the corresponding slope values as one value of a coordinate on the coordinate system; performing regression calculation based on the plurality of plotted points to obtain a regression function equation of a graph corresponding to the plurality of plotted points; and displaying a graph corresponding to the regression function equation obtained by the regression calculation on the display.