How to Fill in Empty Matrix in R with Loop [duplicate] - r

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Reshape dataframe and create similarity matrix
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Closed 7 years ago.
I have a blank matrix called Trial that is 5000 X 5000, but i'll put a small snippet.
a b c d e f
a
b
c
d
e
f
and I want to fill the Matrix, with a Data Table I have.
Name Value
-----------
Cat A
Cat B
Cat E
Dog D
Dog C
Dog F
So basically in the end, I want the matrix to be filled like this:
a b c d e f
a 1 1 0 0 1 0
b 1 1 0 0 1 0
c 0 0 1 1 0 1
d 0 0 1 1 0 1
e 1 1 0 0 1 0
f 0 0 1 1 0 1
So all the values relating to the Name will be 1, and if they don't relate they will be 0. For example, A and F don't relate because they are different names (cat and dog), thus they will get a 0.

Answer 1

Here is a way with loops
dd <- read.table(header = TRUE, text="Name Value
Cat A
Cat B
Cat E
Dog D
Dog C
Dog F")
o <- order(dd$Value)
sapply(1:nrow(dd), function(x) dd$Name %in% dd[x, 'Name'] + 0L)[o, o]
# [,1] [,2] [,3] [,4] [,5] [,6]
# [1,] 1 1 0 0 1 0
# [2,] 1 1 0 0 1 0
# [3,] 0 0 1 1 0 1
# [4,] 0 0 1 1 0 1
# [5,] 1 1 0 0 1 0
# [6,] 0 0 1 1 0 1
or with an explicit for loop
mm <- matrix(nrow = nrow(dd), ncol = nrow(dd))
for (ii in 1:nrow(mm))
mm[ii, ] <- dd$Name %in% dd[ii, 'Name'] + 0L
mm[o, o]
For 5000 x 5000, takes less than 2 seconds on my crummy laptop
dd <- data.frame(Name = sample(LETTERS, 5000, replace = TRUE), Value = 1:5000)
o <- order(dd$Value)
system.time({
oo <- sapply(1:nrow(dd), function(x) dd$Name %in% dd[x, 'Name'] + 0L)[o, o]
})
# user system elapsed
# 1.680 0.188 1.874
system.time({
mm <- matrix(nrow = nrow(dd), ncol = nrow(dd))
for (ii in 1:nrow(mm))
mm[ii, ] <- dd$Name %in% dd[ii, 'Name'] + 0L
mm[o, o]
})
# user system elapsed
# 1.918 0.152 2.073