将一年中的每一天的天数列转换为365个指标变量

Question

I have a data frame like the one generated below. The id column is not unique I also have a data frame of 365 columns, one for each day. The "day" column represents the day of the year. I would like each row of the second data frame to map to the id column with 1s for the days that are present with that id and 0s otherwise. The data are not ordered neatly like in the example data frame.

data <- data.frame(id = 1:100, day = as.integer(runif(100, 0, 364)))

The expected output for an id that had the values 0, 3, and 364 in the original data frame would be:

    id day0 day1 day2 day3 ... day364
     1    1    0    0    1          1

I am also open to solutions that involve using data.table . Thank you!

Answer 1

Per my comment, you just want a crosstable, which can be obtained with:

tab <- with(data,table(id, day))

If you just want that table to show presence/absence of matches (ie, a cell should be 1 even if multiple entries correspond to the same id/day pair), then just convert tab with the following:

tab[tab>=1] <- 1

Answer 2

Just for fun here's an alternate solution:

library(reshape2)
dcast(data, id ~ day, is.integer, fill =0)