Question

Let say I have the following data frame in R:

df1 <- data.frame(Item_Name = c("test1","test2","test3"), D_1=c(1,0,1),
                  D_2=c(1,1,1), D_3=c(11,3,1))

I would like to create a function that would delete columns with no variance
(e.g. in this case, it would remove column D_2 because it has only 1 value)

I know that I could check it by hand, but in reality my data is very large and I would like to automate it. Any idea?

Answer 1

Filter is a useful function here. I will filter only for those where there is more than 1 unique value.

i.e.

Filter(function(x)(length(unique(x))>1), df1)

##   Item_Name D_1 D_3
## 1     test1   1  11
## 2     test2   0   3
## 3     test3   1   1