contourc – Low-level contour plot computation
C = contourc(Z)
computes the contour matrix from data in matrix Z, where Z must be at least a 2-by-2 matrix. The contours are isolines（等值线） in the units of Z. The number of contour lines and the corresponding values of the contour lines are chosen automatically.
- C is a two-row matrix specifying all the contour lines.
- Each contour line defined in matrix C begins with a column that contains the value of the contour (specified by v and used by clabel), and the number of (x,y) vertices in the contour line.
- The remaining columns contain the data for the(x,y) pairs.
C = [value1 xdata(1) xdata(2) ... xdata(dim1) value2 xdata(1) xdata(2) ... xdata(dim2)... dim1 ydata(1) ydata(2) ... ydata(dim1) dim2 ydata(1) ydata(2) ... ydata(dim2)];
Specifying irregularly spaced x and y vectors is not the same as contouring irregularly spaced data. If x or y is irregularly spaced, contourc calculates contours using a regularly spaced contour grid, then transforms the data to x or y.