[R] dplyr and function length()

[Karl Schilling]

Dear All,

I have an observation / question about how the function length() works 
once package dplyr is loaded.

Say we have a data.frame  df with n rows and m columns. Then a way to 
get the number of rows is to use

length(df$m1)  (m1 here stand is as the header of the first column)

or, alternatively

length(df[,1]).

Both commands will return n.

However, once dplyr is loaded,

length(df[,1]) will return a value of 1.

length(df$m1) and also length(df[[1]]) will correctly return n.

I know that using length() may not be the most elegant or efficient way 
to get the value of n. However, what puzzles (and somewhat disturbs) me 
is that loading of dplyr affects how length() works, without there being 
a warning or masking message upon loading it.

Any clarification or comment would be welcome.

Thank you so much,

Karl


-- 
Karl Schilling