[R] Populating then sorting a matrix and/or data.frame

[Peter Langfelder]

On Thu, Nov 11, 2010 at 1:19 PM, William Dunlap <wdunlap at tibco.com> wrote:
> Peter,
>
> Your example doesn't work for me unless I
> set options(stringsAsFactors=TRUE) first.
> (If I do set that, then all columns of 'results'
> have class "character", which I doubt the user
> wants.)

You probably mean stringsAsFactors=FALSE.

What you say makes sense, because the c() function produces a vector
in which all components have the same type, wnd it will be character.
If you don't want to have characters, my solution would be

n = 10
results <- data.frame(a = rep("", n), b = rep(0, n), c = rep(0, n), d
= rep(0, n))
for(i in 1:n){
   a = LETTERS[i];
   b = i;
   c = 3*i + 2
   d = rnorm(1);
   results$a[i] = a
   results$b[i] = b
   results$c[i] = c
   results$d[i] = d
}

> results
   a  b  c           d
1  A  1  5 -1.31553805
2  B  2  8  0.09198054
3  C  3 11 -0.05860804
4  D  4 14  0.77796136
5  E  5 17  1.28924697
6  F  6 20  0.47631483
7  G  7 23 -1.23727076
8  H  8 26  0.83595295
9  I  9 29  0.69435349
10 J 10 32 -0.30922930

> mode(results[, 1])
[1] "character"
> mode(results[, 2])
[1] "numeric"
> mode(results[, 3])
[1] "numeric"
> mode(results[, 4])
[1] "numeric"



or alternatively

n = 10
num <- data.frame(b = rep(0, n), c = rep(0, n), d = rep(0, n))
labels = rep("", n);
for(i in 1:n){
   a = LETTERS[i];
   b = i;
   c = 3*i + 2
   d = rnorm(1);
   labels[i] = a
   num[i, ] = c(b, c, d)
}
results = data.frame(a = labels, num)

> results
   a  b  c           d
1  A  1  5 -0.47150097
2  B  2  8 -1.30507313
3  C  3 11 -1.09860425
4  D  4 14  0.91326330
5  E  5 17 -0.09732841
6  F  6 20 -0.75134162
7  G  7 23  0.31360908
8  H  8 26 -1.54406716
9  I  9 29 -0.36075743
10 J 10 32 -0.23758269
> mode(results[, 1])
[1] "character"
> mode(results[, 2])
[1] "numeric"
> mode(results[, 3])
[1] "numeric"
> mode(results[, 4])
[1] "numeric"


Peter