# Surface Plots

Surface plots are used to plot (x,y ,z) points in three-dimensional space as a surface where z is interpreted as the height above the xy-plane. A Gnumeric chart of course shows the projection of this surface in 3-space onto a 2-dimensional sheet.

Surface plot sub-types provide for 2 distinct ways of providing the data for a surface plot.

The first subtype uses an n by 1 or 1 by n range for the x-values, a second 1 by m or m by 1 range for the y-values and an m by n range for the z values. The plotted points are constructed from these three ranges in such a way that the z value in the ith column and jth row is combined with the ith x value and the jth y value. This subtype then uses an m by n grid for the surface.

Figure 10-12An example of a surface plot with rectangular data area

The second subtype uses a direct listing of the n points. The x values are specified with an n by 1 range, so are the y and z values. The ith z value is then combined with the ith x and ith y value to obtain the points to be plotted.It is not necessary to provide the same number of y coordinates for each x coordinate or vice versa. Gnumeric will interpolate missing values. For this purpose one needs to specify the number of (equidistant) rows and columns to be used for the surface grid. This grid need not align with the provided coordinates.

Figure 10-13An example of a surface plot with x,y, and z series

Surface plots do not have any pre-defined styles.

Table 10-9The data in each surface plot series with rectangular data area
Element Type Example
Name A single textual element labeling the data series. These will be used in the legend which may be displayed with the surface plot. {"Widgets"}
X An optional series of numeric values to be used for the x coordinates of the grid. This defaults to {1,2,…,n}. {1,3,5,6,8,9}
Y An optional series of numeric values to be used for the y coordinates of the grid. This defaults to {1,2,…,n}. {1,1.5,2,2.5}
Z A rectangular range of numbers where the number in jth row and ith column is the height of the (i,j) grid point. A2:J15
Table 10-10The data in each surface plot series with xyz series.
Element Type Example
Name A single textual element labeling the data series. These will be used in the legend which may be displayed with the surface plot. {"Widgets"}
X A series of numeric values to be used for the x coordinates of the grid. {1,1.5,2,2.5}
Y A series of numeric values to be used for the y coordinates of the grid. {1,1.5,2,2.5}
Z A series of numeric values to be used for the z coordinates of the grid. {1,1.5,2,2.5}

Surface plots provide two icons to choose one of the two surface plot sub-types.

Surface plot sub-type and style options.

The icon for an area plot of the sub-type with rectangular data area.

The icon for an area plot of the sub-type with xyz series.