Return value at deepest point in dataset

[HABSaremyjam]

Hello contributors!

I have a water quality dataset where I am trying to have R return the value of DO at the deepest point in the water column. For example, in the below dataset, at depth 11, the DO is 2.00. I want R to do that automatically and to set that value to BOTTOM_DO.

df <- structure(list(X = 1:13, SITE_ID = c("GBA20-10501", "GBA20-10501", 
"GBA20-10501", "GBA20-10501", "GBA20-10501", "GBA20-10501", "GBA20-10501", 
"GBA20-10501", "GBA20-10501", "GBA20-10501", "GBA20-10501", "GBA20-10501", 
"GBA20-10501"), DEPTH = c(0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 
10, 11), LINE = c(13.5, 13.5, 13.5, 13.5, 13.5, 13.5, 13.5, 13.5, 
13.5, 13.5, 13.5, 13.5, 13.5), TEMPERATURE = c(21.95, 21.9, 21.9, 
21.85, 21.7, 21.65, 21.55, 21.3, 20.35, 18.3, 16.8, 15.95, 15.7
), DO = c(9.6, 9.6, 9.7, 9.55, 9.45, 9.3, 8.95, 8.6, 6.55, 4.85, 
2.35, 2.05, 2), PH = c(8.64, 8.64, 8.645, 8.64, 8.62, 8.6, 8.565, 
8.485, 8.255, 8.06, 7.955, 7.94, 7.935), CONDUCTIVITY = c(309.75, 
309.75, 309.75, 309.6, 310.05, 310.65, 310.35, 310.6, 309, 299.95, 
292.55, 287.55, 287.8), LIGHT_AMB = c(204.15, 204.35, 204.2, 
204.15, 204.25, 204.3, 204.25, 204.15, 204.4, 204.1, 204.15, 
204.2, 204.15), LIGHT_UW = c(985.4, 853.1, 834.5, 332.65, 124.7, 
64.55, 31.1, 15.05, 7.65, 3.8, 2.25, 0.9, 0.25)), row.names = c(NA, 
13L), class = "data.frame", na.action = structure(c(`14` = 14L), class = "omit"))
>

I can figure out the deepest point using:

max(df$DEPTH, na.rm=T)

But I'm not having much luck figuring out how to use this value to obtain the DO at the point.

Thanks so much for your help!

[Jwvz001]

Hi,

Use which() to return the index. In your case I guess

df$DO[which.max(df$DEPTH)]
[1] 2

JW

[HABSaremyjam]

Thank yooooou - I know about the which() function but I couldn't figure out how to apply it. Much appreciated!