[R] Question about addressing a data frame

[Nitu, Laurentiu]

Hello,


I have this data frame [algae] in the package DMwR. I thought I understand how to refer an element but I cannot explain...

is.na(algae) is giving us the a logical vector with TRUE being the na's.
which(is.na(algae)) gives the positions on the elements in the data frame where is.na returns TRUE.


However which(is.na(algae)) returns


[1]  648  838  862 1055 1056 1057 1058 1059 1060 1061 1062 1161 1199 1262 1399 1462 1599 1662 1799 1828 1999 2055 2056 2057 2058 2059 2060 2061 2062 2063
[31] 2116 2184 2199

Weirs since:


> dim(algae)

[1] 200  18


If I refer back algae[which(is.na(algae))) I get a vector of NA's...

What are the values returned by which(is.na(algae))?

Thanks a lot for your help

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