[R] how to pass additional parameters to a function called in tapply?

[jim holtman]

try:

tapply(data,factor-vectors,avg.f, part)

On Mon, Sep 1, 2008 at 1:41 PM, Wolfgang Waser <wolfgang.waser at utu.fi> wrote:
> Hi all,
>
> the following problem is still beyond my R-knowledge:
>
> I have one data vector containing the signal from 4 channels that are measured
> subsequently and in repeating cycles (with one factor vector for cycle and
> one for channel identification).
>
> To extract the mean of each channel during each cycle tapply is the method of
> choice. However, I cannot use the whole measuring period for each channel as
> marked in the factor vector since the hardware switching between channels
> causes some transients in the signal which should not be included when
> calculating the mean.
>
>
> Instead of using "mean" as function within tapply, I used the following set of
> functions:
>
>
> start_end.f <- function(x) { c(length(x)*(1-part),length(x)) }
>
>
> to define the part of the data to use (e.g. part=0.5 the last 50% of the total
> period),
>
> #(part has so far been set universally once for the whole analysis, but see
> below)#
>
>
> avg.f <- function(x) {
>  range <- start_end.f(x)
>  mean(x[range[1]:range[2]])
> }
>
>
> and then
>
>
> tapply(data,factor-vectors,avg.f)
>
>
> to extract the mean of a subsample of the total measuring period of each
> channel.
>
>
> The problem now is that I have several signals and different 'parts' should be
> analysed for each, so functions have to be changed to
>
> start_end.f <- function(x,part) { ... }
>
> avg.f <- function(x,part)
>  range <- start_end.f(x,part)
>  mean(x[range[1]:range[2]])
> }
>
>
> However, this causes an error
>
>
> Error in FUN(X[[1L]], ...) : argument "part" is missing, with no default <-
>
>
> since tapply seems to be unable to pass more than x to the function called
>
>
>
> Is there a way to pass variables to the function called in tapply other than
> the dataset extracted by tapply?
>
>
>
> Thanks for any help
>
> Wolfgang
>
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>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?