**Creating a surface plot**

To create a surface plot:

• Define a matrix of values to plot. Mathcad will use the rows and column numbers of the matrix as x- and y-axes. The matrix elements will be plotted as heights above or below the plane.

• Choose Graphic Surface Plot from the Insert menu. Mathcad shows a box with a single placeholder, as shown below:

• Type the name of the matrix in the placeholder. Just as with an equation, Mathcad will not process the surface plot until you click outside the plot.

What you see is a visual representation of the matrix. Mathcad draws a perspective view of the matrix as a two-dimensional grid lying flat in three-dimensional space. Each matrix element is represented as a point at a specified height above or below this grid. The height is proportional to the value of the matrix element. In the default perspective, the first row of the matrix extends from the back left corner of the grid to the right, while the first column extends from the back left corner out toward the viewer. Mathcad draws lines to connect the points in the plot. These lines define. the surface. The perspective for this rendering of the surface depends on the location of the viewer with respect to the surface. You can specify this view by changing the plot’s tilt or rotation, as described in “Changing your view of the surface plot” on page 520.

**Plotting a function of two variables**

A typical surface plot shows the values of a function of two variables. To see such a plot, you must first create a matrix that holds the values of the function, then create a surface plot of that matrix. Here are the typical steps in plotting a function of two variables:

• Define a function of two variables

• Decide how many points you want to plot in the x and y directions. Set up range variables i and j to index these points. For example, if you want to plot 10 points in each direction, enter:

i:= 0 .. 9 j :=0 .. 9

• Define xi and Yj as evenly spaced points on the x- and y-axes.

• Fill the matrix M with the values off( xi’ Yj ).

• Choose Graph-e-Surface Plot from the Insert menu.

• Type M in the placeholder and click outside the region