如何将每行中值> 0的列添加到R中的表中？

Question

I have a table containing data that looks somewhat like this:

treatment, species1, species2, ... 
A, 3, 4, ... 
B, 2, 5, ...

I want to calculate the number of species per row and add the numbers calculated as a new column to the table, to make it look like this:

treatment, species1, species2, ... , number_of_species
A,         3,        4,        ... , 6
B,         2,        5,        ... , 9

I hope you understand what I aim at. As I'm new to R, I tried for some time and didn't find out, so help would be appreciated!

Thanks in advance, Peter

Answer 1

Try something like this. It might take some tweaking to fit your data (it helps to provide some sample data with your question), but this should get you most of the way there.

# An easy way to make sample data
dat <- data.frame(treatment = letters[1:5],
                  species1 = c(3, 4, 0, 1, 3),
                  species2 = c(2, 1, 0, 0, 7),
                  species3 = c(0, 4, 0, 1, 0))

# First step: dat[ , -1] > 0 indicates which values are greater than zero
# You want to exclude the first column, since that just indicates 
# treatment group
dat[ , -1] > 0

# rowSums counts the number of values > 0 in each row - that's because, in R,
# you can add TRUE values to count them
rowSums(dat[ , -1] > 0)

# Finally, wrap it all up and add it to your data.frame
dat$number_of_species <- rowSums(dat[ , -1] > 0)

Answer 2

根据表的存储方式（如果它是table的结果，这应该直接工作，但如果是数据框或其他结构则需要进行一些调整），但它可以很简单：

newtable <- addmargins(mytable, 1, FUN = function(x) sum( x > 0 ) )