Fill lower matrix with vector by row, not column

Question

I am trying to read in a variance-covariance matrix written out by LISREL in the following format in a plain text, whitespace separated file:

 0.23675E+01  0.86752E+00  0.28675E+01 -0.36190E+00 -0.36190E+00  0.25381E+01
-0.32571E+00 -0.32571E+00  0.84425E+00  0.25598E+01 -0.37680E+00 -0.37680E+00
 0.53136E+00  0.47822E+00  0.21120E+01 -0.37680E+00 -0.37680E+00  0.53136E+00
 0.47822E+00  0.91200E+00  0.21120E+01

This is actually a lower diagonal matrix (including diagonal):

 0.23675E+01  
 0.86752E+00  0.28675E+01 
-0.36190E+00 -0.36190E+00  0.25381E+01
-0.32571E+00 -0.32571E+00  0.84425E+00  0.25598E+01 
-0.37680E+00 -0.37680E+00  0.53136E+00  0.47822E+00  0.21120E+01 
-0.37680E+00 -0.37680E+00  0.53136E+00  0.47822E+00  0.91200E+00  0.21120E+01

I can read in the values correctly with scan() or read.table(fill=T).

I am however not able to correctly store the read-in vector in a matrix. The following code

S <- diag(6)
S[lower.tri(S,diag=T)] <- d

fills the lower matrix by column, while it should fill it by row.

Using matrix() does allow for the option byrow=TRUE, but this will fill in the whole matrix, not just the lower half (with diagonal).

Is it possible to have both: only fill the lower matrix (with diagonal) and do it by row?

(separate issue I'm having: LISREL uses 'D+01' while R only recognises 'E+01' for scientific notation. Can you change this in R to accept also 'D'?)

Answer 1

Just read it into the upper triangular portion, rather than the lower:

S <- diag(6)
S[upper.tri(S, diag=TRUE)] <- d
t(S)

Answer 2

The sem package has a very nice function, read.moments() that is designed to do just this:

foo <- read.moments()
 0.23675E+01  
 0.86752E+00  0.28675E+01 
-0.36190E+00 -0.36190E+00  0.25381E+01
-0.32571E+00 -0.32571E+00  0.84425E+00  0.25598E+01 
-0.37680E+00 -0.37680E+00  0.53136E+00  0.47822E+00  0.21120E+01 
-0.37680E+00 -0.37680E+00  0.53136E+00  0.47822E+00  0.91200E+00  0.21120E+01

foo[upper.tri(foo)] <- t(foo)[upper.tri(foo)]

This gives you:

         X1       X2       X3       X4       X5       X6
X1  2.36750  0.86752 -0.36190 -0.32571 -0.37680 -0.37680
X2  0.86752  2.86750 -0.36190 -0.32571 -0.37680 -0.37680
X3 -0.36190 -0.36190  2.53810  0.84425  0.53136  0.53136
X4 -0.32571 -0.32571  0.84425  2.55980  0.47822  0.47822
X5 -0.37680 -0.37680  0.53136  0.47822  2.11200  0.91200
X6 -0.37680 -0.37680  0.53136  0.47822  0.91200  2.11200

---

EDIT1: As for the problem with scan(), just because it was originally printed as a lower triangle doesn't mean you have to put it in the lower triangle:) Just put it in the upper:

foo <- scan()
 0.23675E+01  
 0.86752E+00  0.28675E+01 
-0.36190E+00 -0.36190E+00  0.25381E+01
-0.32571E+00 -0.32571E+00  0.84425E+00  0.25598E+01 
-0.37680E+00 -0.37680E+00  0.53136E+00  0.47822E+00  0.21120E+01 
-0.37680E+00 -0.37680E+00  0.53136E+00  0.47822E+00  0.91200E+00  0.21120E+01

bar <- matrix(0,6,6)

bar[upper.tri(bar,diag=TRUE)] <- foo

bar[lower.tri(bar)] <- t(bar)[lower.tri(bar)]

---

EDIT2: As for the problem with D notation, if I understand it correctly, can be fixed by first scanning characters, gsub the D to E and coerce as numeric:

foo <- scan(what="character")
 0.23675D+01  
 0.86752D+00  0.28675D+01 
-0.36190D+00 -0.36190D+00  0.25381D+01
-0.32571D+00 -0.32571D+00  0.84425D+00  0.25598D+01 
-0.37680D+00 -0.37680D+00  0.53136D+00  0.47822D+00  0.21120D+01 
-0.37680D+00 -0.37680D+00  0.53136D+00  0.47822D+00  0.91200D+00  0.21120D+01


bar <- matrix(0,6,6)

bar[upper.tri(bar,diag=TRUE)] <- as.numeric(gsub("D","E",foo))

bar[lower.tri(bar)] <- t(bar)[lower.tri(bar)]

bar