R Sum complete cases of two columns
Question
How can I sum the number of complete cases of two columns?
With c
equal to:
a b
[1,] NA NA
[2,] 1 1
[3,] 1 1
[4,] NA 1
Applying something like
rollapply(c, 2, function(x) sum(complete.cases(x)),fill=NA)
I'd like to get back a single number, 2
in this case. This will be for a large data set with many columns, so I'd like to use rollapply
across the whole set instead of simply doing sum(complete.cases(a,b))
.
Am I over thinking it?
Thanks!
Solution
You can calculate the number of complete cases in neighboring matrix columns using rollapply
like this:
m <- matrix(c(NA,1,1,NA,1,1,1,1),ncol=4)
# [,1] [,2] [,3] [,4]
#[1,] NA 1 1 1
#[2,] 1 NA 1 1
library(zoo)
rowSums(rollapply(is.na(t(m)), 2, function(x) !any(x)))
#[1] 0 1 2
OTHER TIPS
Did you try sum(complete.cases(x))
?!
set.seed(123)
x <- matrix( sample( c(NA,1:5) , 15 , TRUE ) , 5 )
# [,1] [,2] [,3]
#[1,] 1 NA 5
#[2,] 4 3 2
#[3,] 2 5 4
#[4,] 5 3 3
#[5,] 5 2 NA
sum(complete.cases(x))
#[1] 3
To find the complete.cases()
of the first two columns:
sum(complete.cases(x[,1:2]))
#[1] 4
And to apply
to two columns of a matrix
across the whole matrix you could do this:
# Bigger data for example
set.seed(123)
x <- matrix( sample( c(NA,1:5) , 50 , TRUE ) , 5 )
# [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
#[1,] 1 NA 5 5 5 4 5 2 NA NA
#[2,] 4 3 2 1 4 3 5 4 2 1
#[3,] 2 5 4 NA 3 3 4 1 2 2
#[4,] 5 3 3 1 5 1 4 1 2 1
#[5,] 5 2 NA 5 3 NA NA 1 NA 5
# Column indices
id <- seq( 1 , ncol(x) , by = 2 )
[1] 1 3 5 7 9
apply( cbind(id,id+1) , 1 , function(i) sum(complete.cases(x[,c(i)])) )
[1] 4 3 4 4 3
complete.cases()
works row-wise across the whole data.frame
or matrix
returning TRUE
for those rows which are not missing any data. A minor aside, "c"
is a bad variable name because c()
is one of the most commonly used functions.
This shoudl work for both matrix
and data.frame
> sum(apply(c, 1, function(x)all(!is.na(x))))
[1] 2
and you could simply iterate through large matrix M
for (i in 1:(ncol(M)-1) ){
c <- M[,c(i,i+1]
agreement <- sum(apply(c, 1, function(x)all(!is.na(x))))
}