how to drop columns by passing variable name with dplyr?

You can simple use

a <- data_frame(keep=c("hello", "world"),drop = c("nice", "work"))
select(a, -starts_with('drop'))
#   Source: local data frame [2 x 1]
#
#   keep
#   (chr)
# 1 hello
# 2 world

you have to search for some previously written solutions too. Please read the document here Select/rename variables by name.DPLYR

I hope that does the job for you :) @Psidom thanx for updating your answer.. but I will request upvoters for vote for me too as I recently became an active user and still am to get basic privileges on stackoverflow.

We can use select with setdiff

a %>%
    select_(setdiff(names(.), name))
# A tibble: 2 × 1
#   keep
#   <chr>
#1 hello
#2 world

You can use one_of to find the column positions and then use - to drop it, select(-one_of(name)), if you check ?select, the usage is documented in the Drop variable section in the Examples:

name <- "drop"
a %>% select(-one_of(name))

# A tibble: 2 × 1
#   keep
#  <chr>
#1 hello
#2 world

---

Or with select_, you need to paste - with the column names to drop them and pass the pasted column names to the .dots parameter if there are more than one column to be dropped:

name <- "drop"
a %>% select_(.dots = paste("-", name))

# A tibble: 2 × 1
#   keep
#  <chr>
#1 hello
#2 world