Count number of columns by a condition (>) for each row

Question

I am trying to work out for each row of a matrix how many columns have values greater than a specified value. I am sorry that I am asking this simple question but I wasn\'t

Answer 1

With dplyr package, you can try the following two solutions.

library(dplyr)
df <- as.data.frame(data)

Options 1

df %>%
  mutate(yr.above = rowSums(select(df, `1990`:`1992`) > 30))

Options 2

After dplyr 1.0.0, you can use c_across() with rowwise() to make it easy to perform row-wise aggregations.

df %>%
  rowwise() %>%
  mutate(yr.above = sum(c_across(`1990`:`1992`) > 30)) %>%
  ungroup()

Note: One of the benefits for using dplyr is the support of tidy selections, which provide a concise dialect of R for selecting variables based on their names or properties.

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Output

# # A tibble: 5 x 4
#   `1990` `1991` `1992` yr.above
#            
# 1     25     23     20        0
# 2     22     28     20        0
# 3     35     33     30        2
# 4     42     40     41        3
# 5     44     45     43        3