Michael Knudsen wrote:
On Fri, Jul 24, 2009 at 9:32 AM, Jan Wiener<jan.wie...@tuebingen.mpg.de> wrote:
x=sample(1:5, 115, replace=TRUE)
How do I downsample this vector to 100 entries? Are there any R
functions or packages that provide such functionality.
What exactly do you mean by downsampling?
It means that the original 115 points should be treated as a continuous
function of x, or t, or whatever the horizontal axis is, with new values
coming from this function at 100 evenly-spaced points along this function.
This procedure is how a sound editing program can produce a
good-sounding 44.1 kHz CD quality file from material recorded at 48 kHz,
for instance. Something similar happens when you ask your photo editing
program to give you a smaller version of, say, a 12 Mpix picture for
emailing or putting up on the web. These are all forms of interpolation.
There's a degenerate case, where the number of output samples divides
evenly into the number of input samples. For instance, to downsample a
96 kHz audio file to 48 kHz, just throw away every other sample.
I, too, wish I know how to do the harder interpolation case in R. I've
been in the OP's shoes, fighting with zoo and failing. The last time I
had to do this, I gave up on R and did it in Mathematica. I also
remember that it was easy to do this in Igor Pro when I played with its
demo version.
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