如何在R中创建一个填充了1和0的表，以显示来自另一个表的值的存在？

Question

I'm working with data regarding people and what class of medicine they were prescribed. It looks something like this (the actual data is read in via txt file):

test <- matrix(c(1,"a",1,"a",1,"b",2,"a",2,"c"),ncol=2,byrow=TRUE)
colnames(test) <- c("id","med")
test <- as.data.table(test)
test <- unique(test[, 1:2])
test

The table has about 5 million rows, 45k unique patients, and 49 unique medicines. Some patients have multiples of the same medicines, which I remove. Not all patients have every medicine. I want to make each of the 49 unique medicines into separate columns, and have each unique patient be a row, and populate the table with 1s and 0s to show if the patient has the medicine or not.

I was trying to use spread or dcast, but there's no value column. I tried to amend this by adding a row of 1s

test$true <- rep(1, nrow(test))

And then using tidyr

library(tidyr)
test_wide <- spread(test, med, true, fill = 0)

My original data produced this error but I'm not sure why the new data isn't reproducing it...

Error: `var` must evaluate to a single number or a column name, not a list

Please let me know what I can do to make this a better reproducible example sorry I'm really new to this.

Answer 1

Another solution using dplyr

library(dplyr)
test %>% group_by(id) %>% table()

Answer 2

It looks like you are trying to do onehot encoding here. For this please refer to the "onehot" package. Details are here .

Code for reference:

library(onehot)
test <- matrix(c(1,"a",1,"a",1,"b",2,"a",2,"c"),ncol=2,byrow=TRUE)
colnames(test) <- c("id","med")
test <- as.data.frame(test)

str(test)
test$id <- as.numeric(test$id)
str(test)
encoder <- onehot(test)
finaldata <- predict(encoder,test)
finaldata

Make sure that all the columns that you want to be encoded are of the type factor . Also, I have taken the liberty of changing data.table to data.frame .