Figure 4
The three-dimensional surface mesh plot shows how values vary jointly across two horizontal dimensions and one vertical dimension. One horizontal axis is labeled “Shandong Port Cluster” and spans values approximately from 1.25 to 1.6, with evenly spaced tick marks along this range. The second horizontal axis is labeled “year” and runs from 2010 to 2024, marked at two year intervals. The vertical axis ranges from 0.00 to 0.40 in increments of 0.05 units. The surface is rendered as a wireframe grid composed of intersecting curved lines. The grid lines form a smooth, continuous surface that rises and falls across both horizontal dimensions. Near the middle of the “Shandong Port Cluster” range, the surface rises sharply to a broad ridge, reaching its highest values close to 0.38–0.40. Toward lower and higher values of the “Shandong Port Cluster” axis, the surface slopes downward, approaching values near zero at both extremes. Along the “year” axis, the surface shows gradual variation. In earlier years around 2011, values are generally lower across most of the surface. As the years progress toward the middle of the time range, the surface becomes higher and flatter near the central ridge. In later years approaching 2023, the surface gradually declines again, especially toward the right side of the “Shandong Port Cluster” axis. The surface is colored with a gradient transitioning from darker blue tones at lower values to lighter green and yellow tones at higher values, reinforcing the changes in height. A light grid is visible on the background planes, helping to indicate depth and scale. The overall shape resembles a smooth ridge or plateau that peaks in the central region and tapers off toward the edges across both the “Shandong Port Cluster” and “year” dimensions. Note: All numerical data values are approximated.Kernel density distribution of competitiveness level in Shandong port cluster from 2011 to 2023. Source(s): Authors’ own creation