Displaying 20 results from an estimated 10000 matches similar to: "A problem about all possible sequences"
2006 Feb 22
3
elements that appear only once
Hi.
I have a factor and I want to extract just those elements that appear
exactly once.
How to do this?
Toy example follows.
> a <- as.factor(c(rep("oak",5) ,rep("ash",1),rep("elm",1),rep
("beech",4)))
> a
[1] oak oak oak oak oak ash elm beech beech beech beech
Levels: ash beech elm oak
> table(a)
a
ash beech elm oak
2008 Mar 26
5
S4 slot with NA default
Hi
How do I specify an S4 class with a slot that is potentially numeric,
but NA
by default? I want the slot to be NA until I calculate its value
(an expensive operation, not needed for all applications). When
its value is
known, I will create a new object with the correct value inserted in
the slot.
I want "NA" to signify "not known".
My attempt fails because
2006 Sep 13
3
functions and strings
Hi
If
string <- "xyz"
f <- function(x){1 + sin(cos(x)) + exp(x^2)}
How do I manipulate "string" and f() to give the string
"1 + sin(cos(xyz)) + exp(xyz^2)"
?
--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
tel 023-8059-7743
2006 Jul 27
4
inserting rows into a matrix
Hi
I have a little vector function that takes a vector A of strictly
positive integers
and outputs a matrix M each of whose columns is the vector, modified in
a complicated combinatorical way.
Now I want to generalize the function so that A can include zeroes.
Given A,
I want to strip out the zeroes, pass it to my function, and pad M
with rows at positions corresponding to the zeroes
2007 Mar 19
3
character to numeric conversion
Hi.
Is there a straightforward way to convert a character string
containing comma-delimited
numbers to a numeric vector?
In my application, I use
system(executable.string, intern=TRUE)
which returns a string like
"[0.E-38, 2.096751179214927596171268230,
3.678944959657480671183123052, 4.976528845643001020345216157,
6.072390165503099343887569007, 7.007958550337542210168866070,
2005 Nov 17
3
changing figure size in Sweave
Hi
In Sweave, how does one change the size of the plots?
I tried using a hook:
<<echo=FALSE, print=FALSE, fig=TRUE>>=
options(SweaveHooks=list(fig=function() ps.options(width=1)))
library(graphics)
pairs(iris)
@
but this didn't change the size of the figure. How to make the
figures a
different size?
--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre,
2005 Jan 07
1
Visualizing complex analytic functions using domain coloring
Hi
has anyone coded up domain colouring for visualizing complex analytic
functions
(such as elliptic functions)?
[
the idea is to depict a complex function f(z) using a filled.contour()
variant
in which the hue is given by Arg(f(z)), and the saturation by Mod(f(z)).
]
--
Robin Hankin
Uncertainty Analyst
Southampton Oceanography Centre
European Way, Southampton SO14 3ZH, UK
tel
2007 Jun 18
4
triangle contour plots
Suppose I have three numbers p1, p2, p3 with
0 <= p1,p2,p3 <= 1 and p1+p2+p3=1,
and a function f=f(p1,p2,p3) = f(p1,p2,1-p1-p2).
How to draw a contour plot of f() on the p1+p2+p3=1 plane,
that is, an equilateral triangle?
Functions triplot(), triangle.plot(), and ternaryplot() give
only scatterplots, AFAICS
--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre,
2007 Jan 16
5
"[[" gotcha
The following gotcha caught me off-guard just now.
I have two matrices, a and b:
a <- matrix(1,3,3)
b <- matrix(1,1,1)
(note that both "a" and "b" are matrices).
I want them in a list:
> B <- NULL
> B[[1]] <- a
> B[[2]] <- b
> B
[[1]]
[,1] [,2] [,3]
[1,] 1 1 1
[2,] 1 1 1
[3,] 1 1 1
[[2]]
[,1]
[1,] 1
2006 Oct 13
5
combinatorics
Hi
How do I generate all ways of ordering sets of indistinguishable items?
suppose I have two A's, two B's and a C.
Then I want
AABBC
AABCB
AACBC
ABABC
. . .snip...
BBAAC
. . .snip...
CBBAA
[there are 5!/(2!*2!) = 30 arrangements. Note AABBC != BBAAC]
How do I do this?
--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14
2005 Jan 05
4
output from table() in matrix form
Hi
How do I get the output from table() in matrix form?
If I have
R> table(c(1,1,1,1,2,20))
1 2 20
4 1 1
I want
[,1] [,2] [,3]
[1,] 1 2 20
[2,] 4 1 1
The problem is that names(table) is a vector of characters and I need
the numeric values.
I am using
R> rbind(as.integer(names(x)),x)
I thought tabulate() might be better as it takes an
2005 Jun 20
6
sweep() and recycling
Hi
I had a hard-to-find bug in some of my code the other day, which I
eventually
traced to my misusing of sweep().
I would expect sweep() to give
me a warning if the elements don't recycle nicely, but
X <- matrix(1:36,6,6)
sweep(X,1,1:5,"+")
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] 2 9 16 23 30 32
[2,] 4 11 18 25 27 34
[3,] 6 13 20 22
2005 Aug 31
3
generic function argument list problem
Hi
it says in R-exts that
A method must have all the arguments of the generic,
including ... if the generic does.
A method must have arguments in exactly the same order as the
generic.
A method should use the same defaults as the generic.
So, how come the arguments for rep() are (x, times, ...) and the
arguments
for rep.default() are (x, times, length.out, each, ...) ?
2006 Feb 28
2
lines() and recycled colours
Hi
?lines says
For 'type = "h"', 'col' can be a vector and will be recycled as
needed.
Why doesn't lines() recycle colours for other types?
If I type
> plot(0:1,0:1,type="n")
> lines(runif(11),runif(11),col=c("red","green"))
>
then all ten lines are red, with no warning given. Is there a reason
why
2006 May 16
3
sparklines
I am fairly new to R so I don;t know much about manipulating it yet.
I would like to make some sparklines <http://www.edwardtufte.com/
bboard/q-and-a-fetch-msg?msg_id=0001OR&topic_id=1> using R. I have th
pre-compiled R for MacOS on intel. Any help would be greatly
appreciated.
Thanks
Robert
2006 Jul 25
2
pari/gp interface
Hi
I'm developing an R package that
needs to execute some code written in pari/gp.
I've used this before from an R package (elliptic) but the interface
is very
basic: the R function creates a string such as the following:
string <- echo ' ellwp ([ 2+0*I , 0+2*I ], 1+0*I )' | gp -q
And then
system(string)
returns the output from gp which then needs to be text processed
2005 Jun 13
3
extracting components of a list
Hi
how do I extract those components of a list that satisfy a certain
requirement? If
jj <- list(list(a=1,b=4:7),list(a=5,b=3:6),list(a=10,b=4:5))
I want just the components of jj that have b[1] ==4 which in this case
would be the first and
third of jj, viz list (jj[[1]],jj[[3]]).
How to do this efficiently?
My only idea was to loop through jj, and set unwanted components to
NULL,
2006 Nov 17
2
do.call("+", ...)
Hi
How do I make do.call() take "+" as a function for a list of more
than two elements?
Toy problem follows:
f <- function(i){matrix((1:6)^i,2,3)}
# Thus f() returns a matrix of size 2x3; I want to add a whole bunch
of such matrices,
# as in f(1) + f(2) + f(3) + f(4)
# But:
> do.call("+",sapply(1:4,f,simplify=FALSE))
Error in do.call("+",
2004 Jun 11
4
rownames of single row matrices
Hi
I want to extract rows of a matrix, and preserve rownames even if only
one row is selected. Toy example:
R> a <- matrix(1:9,3,3)
R> rownames(a) <- letters[1:3]
R> colnames(a) <- LETTERS[1:3]
R> a
A B C
a 1 4 7
b 2 5 8
c 3 6 9
Extract the first two rows:
R> wanted <- 1:2
R> a[wanted,]
A B C
a 1 4 7
b 2 5 8
rownames come through fine. Now extract just
2006 Dec 14
4
two connected graphs
Hi
I have two datasets, A and B, consisting of two columns of numbers
representing x and y coordinates.
They have 10 and 6 rows respectively.
I want to plot two scattergraphs, one above the other.
The lower graph to contain A (10 points) and the upper
graph to contain B (six points).
The x-axes of the two graphs must line up.
I then want to draw straight lines that connect points
of B to a