Re: [R] bootstrap help
I have a similar question.
I want to generate list of 50 bootstrap samples,
it can be done by:
lapply(1:50,function(i){data[sample(nrow(data),size=nrow(data),replace=TRUE),]})
From these bootstrap samples, I want to work out the Bootstrap estimates,
which is E[y]/E[x].
How can I do it?
' data-data.frame(x=rnorm(49), y=rnorm(49))
t(sapply(1:50,function(i){colMeans(data[sample(nrow(data),size=nrow(data),replace=TRUE),])}))'
These codes will generate mean of column x and mean of column y.
Is y the corresponding of x? because x and y are pair data.
Thank you.
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Re: [R] bootstrap help
Hi:
Does this work?
df - data.frame(x = rnorm(49, mean = 1), y = rnorm(49, mean = 2))
# Generate matrix of bootstrap indices
idx - matrix(sample(1:nrow(df), 50 * nrow(df), replace = TRUE),
nrow = nrow(df))
dim(idx)
# [1] 49 50
# Generate the corresponding x, y, bootstrap samples by using
# matrix indexing by mapping the x and y values to the indices in
# the idx matrix
xboot - matrix(df$x[idx], nrow = nrow(df))
yboot - matrix(df$y[idx], nrow = nrow(df))
# Find respective x, y means from bootstrap samples
xmean.boot - colMeans(xboot)
ymean.boot - colMeans(yboot)
# Take the ratio of the means
xyratio.boot - ymean.boot/xmean.boot
# Now, get bootstrap samples of paired differences
diffboot - yboot - xboot
# Mean differences
diffmean.boot - colMeans(diffboot)
The distribution of the ratio of means is right skewed, whereas the
distribution of the
mean differences looks approximately normal (as one would expect).
Look ma, no [explicit] loops :) More seriously, behold and appreciate the
power of R's (and S's)
indexing capabilities.
HTH,
Dennis
On Wed, Jan 6, 2010 at 9:42 AM, luciferyan anniehyh...@googlemail.comwrote:
I have a similar question.
I want to generate list of 50 bootstrap samples,
it can be done by:
lapply(1:50,function(i){data[sample(nrow(data),size=nrow(data),replace=TRUE),]})
From these bootstrap samples, I want to work out the Bootstrap estimates,
which is E[y]/E[x].
How can I do it?
' data-data.frame(x=rnorm(49), y=rnorm(49))
t(sapply(1:50,function(i){colMeans(data[sample(nrow(data),size=nrow(data),replace=TRUE),])}))'
These codes will generate mean of column x and mean of column y.
Is y the corresponding of x? because x and y are pair data.
Thank you.
--
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Re: [R] bootstrap help
If I read your question now, I think, that I didn't understand you
correctly, but...
My code generates 50 bootstrap samples (50 tables) and for each
calculates mean of column x and mean of column y, so the final result
is matrix with means.
If you don't want to calculate means, code below generates list of 50
bootstrap samples.
lapply(1:50,function(i){data[sample(nrow(data),size=nrow(data),replace=TRUE),]})
Please check help if some functions aren't understandable.
2009/12/7 casperyc caspe...@hotmail.co.uk:
Hi there,
This seems to 'simple' for that. ( I mean the codes are too good)
Can I ask for a bit explaination? or some simplier (maybe few more line
codes) to archieve that goal?
And the codes you gave here,
first line give a table with x and y , random normal values,
but the second line, what does that do?
I totally can't follow that line.
the result is a 50 by 2 table.
what is that? is a sample?
Thanks.
casper
Marek Janad wrote:
data-data.frame(x=rnorm(49), y=rnorm(49))
t(sapply(1:50,function(i){colMeans(data[sample(nrow(data),size=nrow(data),replace=TRUE),])}))
r-help@r-project.org
2009/12/7 casperyc caspe...@hotmail.co.uk:
Hi there,
i think that's not what i was aiming for...
i was aked to
Generate 50 Bootstrap samples and corresponding estimates
if i do data[sample(nrow(data),size=50,replace=TRUE),]
it will give me a table of 50 rows ( 50 sets of x and y)
then how do i estimate the mean? ( mean was esitmated by the
bar{x}/bar{y} )
i mis undertood that too.
but now, i think what i actually need is
50 sets of this kind (49 rows) of tables from bootstrapping
so that i can have 50 different 'bar{x}/bar{y}' s
then to estimate the mean...
Thanks.
casper
Ben Bolker wrote:
casperyc casperyc at hotmail.co.uk writes:
I have 49 pairs in my data.frame 'data'
x y
76 80
... ...
how do I get a bootstrap sample of size n=50?
data[sample(nrow(data),size=50,replace=TRUE),]
__
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and provide commented, minimal, self-contained, reproducible code.
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[R] bootstrap help
Hi, I have 49 pairs in my data.frame 'data' x y 76 80 138 143 67 67 29 50 381 464 23 48 37 63 120 115 ... ... how do I get a bootstrap sample of size n=50? i have tried sample(data,size=50,replace=TRUE) and sample(data,replace=TRUE) both didnt seem to work (the latter one only return me with 49 sample) Thanks. casper -- View this message in context: http://n4.nabble.com/bootstrap-help-tp949807p949807.html Sent from the R help mailing list archive at Nabble.com. __ 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] bootstrap help
casperyc casperyc at hotmail.co.uk writes: I have 49 pairs in my data.frame 'data' x y 7680 ... ... how do I get a bootstrap sample of size n=50? data[sample(nrow(data),size=50,replace=TRUE),] __ 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] bootstrap help
Hi there,
i think that's not what i was aiming for...
i was aked to
Generate 50 Bootstrap samples and corresponding estimates
if i do data[sample(nrow(data),size=50,replace=TRUE),]
it will give me a table of 50 rows ( 50 sets of x and y)
then how do i estimate the mean? ( mean was esitmated by the bar{x}/bar{y} )
i mis undertood that too.
but now, i think what i actually need is
50 sets of this kind (49 rows) of tables from bootstrapping
so that i can have 50 different 'bar{x}/bar{y}' s
then to estimate the mean...
Thanks.
casper
Ben Bolker wrote:
casperyc casperyc at hotmail.co.uk writes:
I have 49 pairs in my data.frame 'data'
xy
76 80
... ...
how do I get a bootstrap sample of size n=50?
data[sample(nrow(data),size=50,replace=TRUE),]
__
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.
--
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Re: [R] bootstrap help
data-data.frame(x=rnorm(49), y=rnorm(49))
t(sapply(1:50,function(i){colMeans(data[sample(nrow(data),size=nrow(data),replace=TRUE),])}))
r-help@r-project.org
2009/12/7 casperyc caspe...@hotmail.co.uk:
Hi there,
i think that's not what i was aiming for...
i was aked to
Generate 50 Bootstrap samples and corresponding estimates
if i do data[sample(nrow(data),size=50,replace=TRUE),]
it will give me a table of 50 rows ( 50 sets of x and y)
then how do i estimate the mean? ( mean was esitmated by the bar{x}/bar{y} )
i mis undertood that too.
but now, i think what i actually need is
50 sets of this kind (49 rows) of tables from bootstrapping
so that i can have 50 different 'bar{x}/bar{y}' s
then to estimate the mean...
Thanks.
casper
Ben Bolker wrote:
casperyc casperyc at hotmail.co.uk writes:
I have 49 pairs in my data.frame 'data'
x y
76 80
... ...
how do I get a bootstrap sample of size n=50?
data[sample(nrow(data),size=50,replace=TRUE),]
__
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.
--
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and provide commented, minimal, self-contained, reproducible code.
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Marek
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[R] bootstrap help
Hi， I have a dataframe with x and y in pairs, ( 49 pairs i.e. 49 rows ) x y 76 80 138 143 67 67 29 50 381 464 23 48 37 63 120 115 how do i generate 50 Bootstrap samples and corresponding estimates? i have tried sample( data, size=50,replace=T) does not seem to be right Thanks. __ 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] bootstrap help
Hi there,
This seems to 'simple' for that. ( I mean the codes are too good)
Can I ask for a bit explaination? or some simplier (maybe few more line
codes) to archieve that goal?
And the codes you gave here,
first line give a table with x and y , random normal values,
but the second line, what does that do?
I totally can't follow that line.
the result is a 50 by 2 table.
what is that? is a sample?
Thanks.
casper
Marek Janad wrote:
data-data.frame(x=rnorm(49), y=rnorm(49))
t(sapply(1:50,function(i){colMeans(data[sample(nrow(data),size=nrow(data),replace=TRUE),])}))
r-help@r-project.org
2009/12/7 casperyc caspe...@hotmail.co.uk:
Hi there,
i think that's not what i was aiming for...
i was aked to
Generate 50 Bootstrap samples and corresponding estimates
if i do data[sample(nrow(data),size=50,replace=TRUE),]
it will give me a table of 50 rows ( 50 sets of x and y)
then how do i estimate the mean? ( mean was esitmated by the
bar{x}/bar{y} )
i mis undertood that too.
but now, i think what i actually need is
50 sets of this kind (49 rows) of tables from bootstrapping
so that i can have 50 different 'bar{x}/bar{y}' s
then to estimate the mean...
Thanks.
casper
Ben Bolker wrote:
casperyc casperyc at hotmail.co.uk writes:
I have 49 pairs in my data.frame 'data'
x y
76 80
... ...
how do I get a bootstrap sample of size n=50?
data[sample(nrow(data),size=50,replace=TRUE),]
__
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.
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and provide commented, minimal, self-contained, reproducible code.
--
Marek
__
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