The first category consisted of potatoes with nearly constant dry matter content across the potato axis. A prediction example of this is shown in Fig. 4a. Note that three replicates of the same potato are shown side by side. The second category consisted of the potatoes where the dry matter content increased from one end of the measurement to the other. Whether this is seen as decrease or increase depends on the direction of measurement, as can be seen in Fig. 4b. The trend shown in Fig. 4b is believed to be the gradient found along the longitudinal axis (perpendicular to equatorial axis)