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Let say you have a list of vector:
L = list()
L[[1]]= c(2,34,6,7,3)
L[[2]]= c(3,4,6,8,1)
names(L[[1]])=c("A","B","C","D","E")
names(L[[2]])=c("A","R","C","D","F")
L
## [[1]]
## A B C D E
## 2 34 6 7 3
##
## [[2]]
## A R C D F
## 3 4 6 8 1
And I want to sum the 2 vectors by the name of each element... Results:
A B C D E F R
5 34 12 15 3 1 4
Thank you
653
The triangle law of the addition of vectors states that two vectors can be added together by placing them together in such a way that the first vector's head joins the tail of the second vector. Thus, by joining the first vector's tail to the head of the second vector, we can obtain the resultant sum vector.
No. For example, if you write the statement s=sum(v), you are calling a function and that is not vectorized code. The function sum may or may not use vectorized code to do the summing, but the function call that you write is just that, a function call—it does not perform an operation on multiple components.
The sum() is a built-in R function that calculates the sum of a numeric input vector. It accepts a numeric vector as an argument and returns the sum of the vector elements. To calculate the sum of vectors in R, use the sum() function.
We can add two vectors together using the + operator. One thing to keep in mind while adding (or other arithmetic operations) two vectors together is the recycling rule. If the two vectors are of equal length then there is no issue.
Another solution using tapply
> tapply(unlist(L), names(unlist(L)), sum)
A B C D E F R
5 34 12 15 3 1 4
EDIT
It will work even if your vectors have different lengths, see the example:
> L = list()
> L[[1]]= 1:10
> L[[2]]= c(3,4,6,8,1)
> names(L[[1]])=LETTERS[1:10]
> names(L[[2]])=c("A","R","C","D","F")
> tapply(unlist(L), names(unlist(L)), sum)
A B C D E F G H I J R
4 2 9 12 5 7 7 8 9 10 4 # IT WORKS!!!
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