### 4.4.2. Plot of 3D Functions

This procedure is similar to X-Y-Z Grid Plot except that instead of reading the grid values from the data matrix, it will produce its own grid from a function and intervals supplied by the user.

All controls except F(X,Y) and Plot Frequency will work in exactly the same way as they do in 3D Plots procedure (see 4.2.2. X-Y-Z Grid Plot). The F(X,Y) field is used for entering a formula in terms of the variables X and Y. No other variable names can be used. Either type the formula directly into the text box or double-click on it to open the Formula Editor dialogue. For the syntax of functions see the beginning of section 4.4. Plot of Functions.

The maximum grid size is 51 x 51. This allows for plotting 50 x 50 surface plots and 51 x 51 bar or point plots.

The Plot Frequency control will regulate the resolution of plots. The highest resolution is obtained when this field is set to 1. In this case the function will be evaluated 50 times for each axis giving a total of 2,500 function evaluations. The lowest resolution is 10, which means that the maximum grid size 50 will be divided by 10, giving 5 polygons (or 5 bars or 5 points) for each axis.

Since computing the grid elements from the supplied function may be a time consuming process, it will not be repeated whenever a graph property is changed. For instance the grid will not be recomputed if changes are made in the main title, sub title, X, Y and Z axis labels, minimum, maximum and interval values of the Z axis, type, rotation, grid and colours fields. If changes are made in one of minimum, maximum X or Y-axis values, the definition of function or the Plot Frequency, then the whole grid will be recomputed.