Comparing array rows

Question

I want to compare the first row of an array with the rest of them. So I am running the following code but the results are not as expected. For example flag[2, 1] is FALSE instead of TRUE (2 > 1). Any idea what I am doing wrong ?

yy <- array(data = c(1:16), dim = c(4,4))
yy
#     [,1] [,2] [,3] [,4]
#[1,]    1    5    9   13
#[2,]    2    6   10   14
#[3,]    3    7   11   15
#[4,]    4    8   12   16

flag <- (yy >= yy[1, ])
flag
#      [,1]  [,2]  [,3] [,4]
#[1,]  TRUE  TRUE  TRUE TRUE
#[2,] FALSE  TRUE  TRUE TRUE
#[3,] FALSE FALSE  TRUE TRUE
#[4,] FALSE FALSE FALSE TRUE

Thank you all.

G. Grothendieck · Accepted Answer · 2015-10-25 21:31:11Z

3

R stores arrays in columns, not in rows. You want:

t(t(yy) >= yy[1,])

Another approach is:

yy >= matrix(yy[1,], nrow(yy), ncol(yy), byrow = TRUE)

edited Oct 25, 2015 at 21:31

answered Oct 25, 2015 at 21:27

G. Grothendieck

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1 Comment

Apostolos Over a year ago

You are right. I didn't know that. Thank you a lot.

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