log10 vs semilog

why does the graph of semilogy(gateVoltage, Draincurrent) not match the graph of plot(gateVoltage, log10(Draincurrent))?

both curves match perfectly in shape, but the semilogy y curve has very small positive y values while the log10 curve has large negative y values.

Answer 1

[William Rose]

@Samantha Cole

In the first case, the actual value Draincurrent is plotted on the vertical axis, and the vertical axis has log scaling.

In the second case, the log of Draincurrent is plotted on the vertical axis, and the vertical axis has linear (i.e. normal) scaling. I assume your DrainCurrent is <1 (and >0), which is why log10(Draincurrent) is negative.