Verdia · Library
Compare plant counts with a consistent sample
Keep a marked sample, a whole-plant count and a missing observation distinct before calculating a change.
Choose what the count represents
A count needs a boundary. Ten marked leaves followed over time form one sample; all visible leaves on the plant form another. Replacing one boundary with the other can create a misleading percentage. Write the sample or counting rule beside each observation before comparing dates.
A small invented counting record
| Record | Date | Counting scope | Visible count | Defined baseline | Not observed in marked sample | Visible / baseline |
|---|---|---|---|---|---|---|
| S-01 | 2026-10-26 | marked sample A | 10 | 10 | 0 | 1 |
| S-02 | 2026-11-09 | marked sample A | 9 | 10 | 1 | 0.9 |
| S-03 | 2026-10-26 | whole plant | 12 | Not defined | Not recorded | Unavailable |
| S-04 | 2026-11-09 | whole plant | 15 | Not defined | Not recorded | Unavailable |
| S-05 | 2026-11-16 | marked sample A | Not recorded | 10 | Not recorded | Unavailable |
The marked sample begins with ten identifiers. At the second observation, nine are visible and one is not observed. Separately, a whole-plant count changes from twelve to fifteen. The final marked-sample observation was not recorded, so its visible count is not zero.
Interpret the two changes separately
For the marked sample, the recorded visible count changes by −1 and the visible fraction of the original ten is 0.9. For the whole-plant count, the recorded change is +3. These statements describe the supplied numbers. They do not establish that a missing leaf died, that three new leaves grew, or that the plant became healthier. Visibility, counting differences and unrecorded information remain possible limitations.
Keep missing information out of the denominator
The whole-plant rows do not define a fixed baseline in this example, so their baseline fractions stay unavailable. The last row has a baseline but no observation, so it also has no observed fraction. Filling either situation with zero would create an observation that was not supplied. Retain the missing state in a table or note instead.
Carry the boundary into the next record
Use the same identifiers or explain a deliberate change in sampling. The local observation tool keeps notes; it does not recognize leaves, maintain a marked cohort or compute the fractions shown here. These are manual review calculations beside the source notes. They support clearer record keeping, not a plant-health score, diagnosis, treatment choice or proof of cause.