R?中一个data.frame的每个变量的累积和。

In my code below, I want to first remove the Variable for which i do not have any value (Ie., F should be removed where all the values are 'NA'). then i am trying to find accumulated values of each Variable. I tried with the following code but i am not getting anything out of it.

library(tidyverse)

set.seed(50)

DF <- data.frame(Days = 1:5, A = runif(5,0,3), S = runif(5,1,6),  F = matrix(NA, 5,1), C = runif(5,2,4))
DF_1 <- gather(DF, -Days, key = "Variable", value = "Value")
DF_2 <- DF_1 %>% 
  filter(Variable == "NA") %>% 
  mutate(cumulative_Sum = cumsum(Value))

输出量

For Variable A I should get something like below- similar for others

> A <- cumsum(DF$A)
> A
[1] 2.126181 3.439161 4.039176 6.340374 7.879859