Conditional sum of data frames in R

dataframe, r

Solution

m1 <- matrix(c(0,1,5,3,1,0,2,0,2),3)
m2 <- matrix(c(3,4,1,2,3,0,2,4,3),3)
m3 <- matrix(c(1,3,1,3,4,2,4,3,3),3)
m4 <- matrix(c(6,0,NA,0,0,4,0,NA,0),3)

msum <- m3 + m4
temp <- m1 + m2 + m3
cond <- is.na(m4) | m4==0

msum[cond] <- temp[cond]

#     [,1] [,2] [,3]
#[1,]    7    8    8
#[2,]    8    8    7
#[3,]    7    6    8

Problem

I want to combine data frames and calculate their sum conditionally depending on the value of one of the data frames. For the example below, if a cell in `df4` is not 0 and not NA, the sum should be `df3 + df4` else the sum should be `df1 + df2 + df3`. ``` > df1 1 2 3 A 0 3 2 B 1 1 0 C 5 0 2 > df2 1 2 3 A 3 2 2 B 4 3 4 C 1 0 3 > df3 1 2 3 A 1 3 4 B 3 4 3 C 1 2 3 ``` The condition depends on this frame: ``` > df4 1 2 3 A 6 0 0 B 0 0 NA C NA 4 0 ``` With the above examples, this is the expected result: ``` > dfsum 1 2 3 A 7 8 8 B 8 8 7 C 7 6 8 ``` How do I do this in R?

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