Hi Jeff,
I have a series of NxM numeric tables I'm doing a quick
mean/variance/t-test etcetera on. The cell t1 [i,j] corresponds exactly
to the cells t2..N [i,j], and so it's perfectly possible to read one
item at a time from each of the 100 files and compute the mean/variance
etcetera on all
On Tue, 2007-04-10 at 13:16 +1000, Duncan Coutts wrote:
Note, that like in your original we read each file twice, once for the
mean and once for the variance.
As an aside, you can calculate both mean and variance in one pass (and
constant space) by calculating the sum of elements 'x', the sum
Thanks, Ketil. I knew I could calcuate the mean in constant space, but
I didn't think about the variance. Much appreciated.
On Tue, 2007-04-10 at 08:30 +0200, Ketil Malde wrote:
On Tue, 2007-04-10 at 13:16 +1000, Duncan Coutts wrote:
Note, that like in your original we read each file
I have a series of NxM numeric tables I'm doing a quick
mean/variance/t-test etcetera on. The cell t1 [i,j] corresponds exactly
to the cells t2..N [i,j], and so it's perfectly possible to read one
item at a time from each of the 100 files and compute the mean/variance
etcetera on all cells that
Hello Jefferson,
Monday, April 9, 2007, 9:34:12 PM, you wrote:
if you have enough memory available, the fastest way is to read file
to memory using bytestring, convert it into array of doubles,
repeating this step for all files. then perform your computations. if
you will try to read 100 files
Thanks for the advice. I'm not so much interested in performance here,
as this is just a one-off. Disk thrashing or not, these files are only
a few hundred K apiece, and I can't imagine that the whole computation
will take more than a few minutes.
My question is more about how to deal with
On Mon, 2007-04-09 at 14:40 -0400, Jefferson Heard wrote:
Thanks for the advice. I'm not so much interested in performance here,
as this is just a one-off. Disk thrashing or not, these files are only
a few hundred K apiece, and I can't imagine that the whole computation
will take more than a
It is indeed! Is that to be found in Control.Monad, I take it?
On Tue, 2007-04-10 at 08:50 +1000, Duncan Coutts wrote:
On Mon, 2007-04-09 at 14:40 -0400, Jefferson Heard wrote:
Thanks for the advice. I'm not so much interested in performance here,
as this is just a one-off. Disk thrashing
On Mon, Apr 09, 2007 at 09:24:30PM -0400, Jefferson Heard wrote:
It is indeed! Is that to be found in Control.Monad, I take it?
It's in the Prelude, so you don't have to import anything to get it.
Stefan
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On Mon, 2007-04-09 at 21:24 -0400, Jefferson Heard wrote:
It is indeed! Is that to be found in Control.Monad, I take it?
Yes. Other common derivatives in that module include:
mapM f as = sequence (map f as)
mapM_ f as = sequence_ (map f as)
forM_ = flip mapM_
forM = flip mapM
however,
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