A graph display apparatus wherein a dynamic invention has the following arrangement. A dynamic graph key in a key input unit is operated by a user and a functional formula subjected to graph calculation and a change range and a change pitch of a coefficient value present in the functional formula input using numeric. symbol keys are stored in a formula register in a RAM (Random Access Memory). When an execution key is operated in a state wherein a coefficient change speed is stored in a register, the coefficient value of the functional formula is sequentially replaced within the change range at the change pitch. Graphic data of the functional formula and corresponding graph formulas with the changes in coefficients are sequentially stored in a plurality of video memory areas in a VRAM (Video Random Access Memory), and graphs and corresponding graph formulas for the changes in coefficients are sequentially read out in accordance with the coefficient change speed to be sequentially switched and displayed on a display unit. When the coefficient present in the formula is changed as a parameter, the graphs corresponding to the formulas are sequentially displayed, thus easily grasping the graph change state with the change in coefficient.

There are provided an electronic computing apparatus having a graph displaying function and a graph displaying method which allow an optimum graph to be quickly displayed. A graph is displayed on a display based on data for displaying the graph inputted from a key input section or the like. When one numeric key selected from among a plurality of numeric keys is specified by a predetermined number of times, a quadrant corresponding to the numeric key is selected from a quadrant selection table and a scale corresponding to the specified number of times is selected from a quadrant scale selection table, redisplaying a part of the graph existing in the selected quadrant on the selected scale. Thus, a desired graph may be quickly displayed by selecting the quadrant and scale of the displayed graph.

In tracing a functional equation, a maximum value of the functional equation and an intersection with another functional equation can be recognized on a graph of the functional equation. Coordinate values of any traced dot may include an intersection point discriminated to be a true intersection point or not. An intersection point between dots to be traced, can be traced with the trace interval changed to be finer than the display interval. The tracing cursor indicates specific points by a change in a color and/or shape of the cursor. A point intersection between different functions is determined on the basis of a difference value between traced values of respective functions.

A compact calculator includes a matrix type display unit and executes a graphic representation of a functional formula. When both the functional formula and an integral range are inputted as information about a definite integral, a judgement is done whether or not an X-value increased while forming a graphic representation is located with the integral range. If this X-value is present within the integral range, then the pixels from the coordinate point (X,Y) to an X-axis are turned on. Thus, the integral range is graphically represented under the above-described process operation.

A graph display apparatus includes a plurality of functional formulas to be displayed as graphs and their coordinate ranges are stored in a memory by operating numeric .multidot. symbol keys on a key input unit. The plurality of stored formulas are displayed on a display unit by operating a "list" key. When a plurality of arbitrary formulas are designated and a "synthesis" key is operated, the graphs of the designated formulas are calculated and displayed on a single coordinate system in accordance with coordinate ranges of the formula which is designated first. When the plurality of arbitrary formulas are designated and a "division" key is operated, the functional formulas are displayed on different coordinate systems in accordance with corresponding coordinate ranges. When the graphs of a plurality of input formulas are calculated and displayed, the individual graphs can be appropriately synthesized or divided and can be displayed in comparison with each other.