Two endpoint signals set the gradient by their difference divided by the distance between them, so a larger signal gap means a steeper gradient. The left signal 6 and right signal 18 give a difference of 12 over 6 m, producing gradient 2 per meter exactly for the stated toy signal ledger; real chemotaxis fields have noisy ligand concentrations, diffusion, receptor adaptation, and imaging/calibration limits.
A chemotaxis gradient starts as two checked endpoint signals. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Read two endpoint signals
The left signal is 6 and the right signal is 18 across 6 m.
18−6=12
Difference divided by separation gives gradient
Signal difference 12 over distance 6 m gives gradient 2 per meter.