[R] apply in apply
Dear list, I need to apply a function on each column of each matrix contained in a list. Consider the following code, x - 1:3 my.data - list(matrix(c(1,2,3,4,5,6),ncol=2), matrix(c(4,5,6,7,8,9),ncol=2)) par(mfrow=c(2,2)) results - sapply(1:length(my.data), function(ii) apply(my.data[[ii]], 2, function(y) plot(x,y) )) # plot is for demonstration purposes It works, but I think this is quite dirty code. Is there a simpler way of achieving this? I was considering recasting the list into a matrix, apply the function to all its columns, and then reshape the result into an array of adequate dimensions, as in: results - sapply(matrix(unlist(my.data),ncol= 2 * length (my.data)), function(y) plot(x,y)) #results - matrix(results, ncol = length(my.data)) # when the actual function is used instead of plot but again it feels a bit twisted. Best regards, baptiste _ Baptiste Auguié Physics Department University of Exeter Stocker Road, Exeter, Devon, EX4 4QL, UK Phone: +44 1392 264187 http://newton.ex.ac.uk/research/emag http://projects.ex.ac.uk/atto __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] apply in apply
I need to apply a function on each column of each matrix contained in
a list. Consider the following code,
x - 1:3
my.data - list(matrix(c(1,2,3,4,5,6),ncol=2),
matrix(c(4,5,6,7,8,9),ncol=2))
par(mfrow=c(2,2))
results - sapply(1:length(my.data),
function(ii) apply(my.data[[ii]], 2, function(y) plot(x,y) ))
#
plot is for demonstration purposes
It works, but I think this is quite dirty code. Is there a simpler
way of achieving this?
The last line can be simplified
results - sapply(my.data, function(x) apply(x,2,sum))
(It is perhaps a little clearer what is going on when you use sum rather
than plot as the example function.)
Regards,
Richie.
Mathematical Sciences Unit
HSL
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Re: [R] apply in apply
Thank you for the suggestions (off-list as well). I think the best
option may eventually be an explicit for loop to make things clearer.
To clarify a bit, I've used the plot function in the example where in
fact it is a numerical integration (which is why I need to pass an
additional variable in the second apply call),
intg - function (y, x)
{
n - length(x)
index - order(x)
dx - diff(sort(x))
z - y[index]
ys - (z[1:(n - 1)] + z[2:n])/2
sum(ys * dx)
}
environment: namespace:PROcess
Thanks again for the suggestions,
baptiste
On 30 May 2008, at 10:02, [EMAIL PROTECTED] wrote:
I need to apply a function on each column of each matrix contained in
a list. Consider the following code,
x - 1:3
my.data - list(matrix(c(1,2,3,4,5,6),ncol=2),
matrix(c(4,5,6,7,8,9),ncol=2))
par(mfrow=c(2,2))
results - sapply(1:length(my.data),
function(ii) apply(my.data[[ii]], 2, function(y) plot
(x,y) ))
#
plot is for demonstration purposes
It works, but I think this is quite dirty code. Is there a simpler
way of achieving this?
The last line can be simplified
results - sapply(my.data, function(x) apply(x,2,sum))
(It is perhaps a little clearer what is going on when you use sum
rather
than plot as the example function.)
Regards,
Richie.
Mathematical Sciences Unit
HSL
--
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R-help@r-project.org mailing list
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and provide commented, minimal, self-contained, reproducible code.
Re: [R] apply in apply
On May 30, 2008, at 5:37 AM, baptiste Auguié wrote:
Thank you for the suggestions (off-list as well). I think the best
option may eventually be an explicit for loop to make things
clearer. To clarify a bit, I've used the plot function in the
example where in fact it is a numerical integration (which is why I
need to pass an additional variable in the second apply call),
intg - function (y, x)
{
n - length(x)
index - order(x)
dx - diff(sort(x))
z - y[index]
ys - (z[1:(n - 1)] + z[2:n])/2
sum(ys * dx)
}
environment: namespace:PROcess
Thanks again for the suggestions,
I think this is where the beauty of ... comes in, the following
should be doing just what you want:
sapply(my.data, apply, 2, intg, x)
More clear? Not sure I can judge that, certainly more concise.
sapply just passes the extra arguments to apply, which then just
passes them to intg.
baptiste
Haris Skiadas
Department of Mathematics and Computer Science
Hanover College
On 30 May 2008, at 10:02, [EMAIL PROTECTED] wrote:
I need to apply a function on each column of each matrix
contained in
a list. Consider the following code,
x - 1:3
my.data - list(matrix(c(1,2,3,4,5,6),ncol=2),
matrix(c(4,5,6,7,8,9),ncol=2))
par(mfrow=c(2,2))
results - sapply(1:length(my.data),
function(ii) apply(my.data[[ii]], 2, function(y) plot
(x,y) ))
#
plot is for demonstration purposes
It works, but I think this is quite dirty code. Is there a simpler
way of achieving this?
The last line can be simplified
results - sapply(my.data, function(x) apply(x,2,sum))
(It is perhaps a little clearer what is going on when you use sum
rather
than plot as the example function.)
Regards,
Richie.
Mathematical Sciences Unit
HSL
__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] apply in apply
Very nice, i really like this one! May confuse non-R users, but that's not a concern here. Thanks a lot, baptiste On 30 May 2008, at 13:19, Charilaos Skiadas wrote: I think this is where the beauty of ... comes in, the following should be doing just what you want: sapply(my.data, apply, 2, intg, x) __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
