How do I find the associated x index for a max y value?

I'm working with a graph that compares load resistance values against power supplied, and I have the max y-value, but I need to find the corresponding x index so I can mark the high point of the graph.

Identifies the max y value: [P_max, index] = max(P); Need to find the corresponding x index so I can plot the max point: [???????] = ???(?) ?

Answer 1

[KSSV]

[P_max, index] = max(P)
iwant = yourvariable(index)

[Matt Rulli]

PERFECT! Thanks so much!!