CODEWITHSUNDEEP
rdot-product
Kevin
Kevin

Reputation: 191

Finding the dot product

I have a set of vectors, l:

l <- list(c(1,0), c(0,1))

and vector v:

v <- c(2,2)

Say I want to find the dot product between the first vector in l and vector v, then the code should be:

l[1] %*% v

yet I get the following error:

Error in l[1] %*% v : requires numeric/complex matrix/vector arguments

if I create a new vector containing the first vector in L, the dot product executes properly. What am I doing wrong for l[1] to not work?

l1 <- l[1]

l1 %*% v # = 2

Upvotes: 1

Views: 147

Answers (1)

akrun
akrun

Reputation: 887671

We need to extract the list element with [[ as l[1] is still a list with one element

l[[1]] %*% v
     [,1]
[1,]    2

To do this on all the elements,

lapply(l, `%*%`, v)
[[1]]
     [,1]
[1,]    2

[[2]]
     [,1]
[1,]    2

Upvotes: 3

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