find maximum value in Filled area 2-D plot

hello

i have an image from a face, i ploted this image using (Filled area 2-D plot),

i attached my result, i wanna find maximum Y from plot(as you see in this image is Y=11)

I coudnt use ''findpeaks'' because my output type from this kind of plot(Area) is 1*92 Area

please heeeelp me