I use the head(d) and tail(d) methods in R package utils a lot - frequently one after the other. So i wrote a simple wrapper for the two functions:
ht <- function(d, m=5, n=m){
# print the head and tail together
cat(" head --> ", head(d,m), "\n", "--------", "\n", "tail --> ", tail(d,n), "\n")
}
And i got some unexpected results ... can someone please help me understand why? (so i can fix it ... or at least understand your solution!).
Some background...
Numeric is fine:
x <- 1:100
ht(x)
As is complex:
ni <- as.complex(1:100)
ht(ni)
and character:
ll <- letters[1:26]
ht(ll)
Matrix loses it's structure, returning [1,1] to [5,5] + [16,1] to [20,5] but as two vectors -- compare:
m <- matrix(1:10, 20)
ht(m)
to:
head(m, 5)
tail(m,5)
I would like to keep the matrix structure, as the utils methods does - is this possible?
Finally (well, there may be more bugs, this is just where i'm up to) data.frames are a mess:
df <- data.frame(num=x[1:26], char=ll)
ht(df)
this yields the following error:
head --> Error in cat(list(...), file, sep, fill, labels, append) :
argument 2 (type 'list') cannot be handled by 'cat'
Steps so far:
As the utils method keeps the matrix tidy when done in bits, I tried to fix the problem with the following edit:
function(d, m=5, n=m){
# print the head and tail together
rb <- rbind(head(d, m), tail(d,n))
if (class(d) == 'matrix'){
len <- nrow(rb)
cat(" head --> ", rb[(1:m),], "\n", "--------", "\n", "tail --> ", rb[((len-n):len),], "\n")
}
else cat(" head --> ", rb[1,], "\n", "--------", "\n", "tail --> ", rb[2,], "\n")
}
Which does not seem to have done anything to the matrix ... and still breaks with the same error when i
ht(df)
I am guessing from the errors that there is some issue with cat() here, but i cannot figure out what it is or how to fix it.
Can anyone please help?