[R] built a lower triangular matrix from dataframe

[nymphita]

Hi David,

What an good solution. It works perfectly and it's really simple. 
(I only removed the "1+" in ncol=1+max(j), it already has 6 columns)
My result has been:

> df <- read.table(file="df.txt", head=T, sep="\t")
> df
   i j   k
1  1 2 5.2
2  1 3 9.1
3  1 4 8.0
4  1 5 2.3
5  1 6 8.4
6  2 3 6.6
7  2 4 7.4
8  2 5 7.1
9  2 6 5.5
10 3 4 4.1
11 3 5 3.9
12 3 6 9.2
13 4 5 8.5
14 4 6 7.6
15 5 6 9.9
> zmat <- with(df, matrix(0, ncol=max(j), nrow=1+max(i) ))
> # Then populate it with:
> zmat[with(df, cbind(i,j)) ] <- with(df, k) 
> zmat
     [,1] [,2] [,3] [,4] [,5] [,6]
[1,]    0  5.2  9.1  8.0  2.3  8.4
[2,]    0  0.0  6.6  7.4  7.1  5.5
[3,]    0  0.0  0.0  4.1  3.9  9.2
[4,]    0  0.0  0.0  0.0  8.5  7.6
[5,]    0  0.0  0.0  0.0  0.0  9.9
[6,]    0  0.0  0.0  0.0  0.0  0.0

Great.

(I only inluded some png images in the post because the matrix looked more
neat to me that way...  It was my first time on Nabble. Thanks for calling
my attention on that, you are right)

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