| aggregate-methods {hyperSpec} | R Documentation |
Computes summary statistics for subsets of a hyperSpec
object.
## S4 method for signature 'hyperSpec':
aggregate(x, by, FUN, ..., out.rows = NULL,
append.rows = NULL,
short = NULL, date = NULL, user = NULL)
x |
a hyperSpec object |
by |
grouping for the rows of x@data.
Either a list containing an index vector for each of the subgroups or a vector that can be split in such a list. |
FUN |
function to compute the summary statistics |
out.rows |
number of rows in the resulting hyperSpec
object, for memory preallocation. |
append.rows |
If more rows are needed, how many should be
appended?
Defaults to 100 or an estimate based on the percentage of groups that are still to be done, whatever is larger. |
... |
further arguments passed to FUN |
short, date, user |
aguments passed to logentry |
aggregate applies FUN to each of the subgroups given by
by. It combines the functionality of
aggregate, tapply, and ave for
hyperSpec objects.
aggregate avoids splitting x@data.
FUN does not need to return exactly one value.
The number of returned values needs to be the same for all
wavelengths (otherwise the result could not be a matrix), see the examples.
If the initially preallocated data.frame turns out to be too
small, more rows are appended and a warning is issued.
A hyperSpec object with an additional column
@data$.aggregate tracing which group the rows belong to.
C. Beleites
## make some "spectra"
spc <- new ("hyperSpec", spc = sweep (matrix (rnorm (10*20), ncol = 20), 1, (1:10)*5, "+"))
## 3 groups
color <- c("red", "blue", "black")
by <- as.factor (c (1, 1, 1, 1, 1, 1, 5, 1, 2, 2))
by
plot (spc, "spc", col = color[by])
## Example 1: plot the mean of the groups
plot (aggregate (spc, by, mean), "spc", col = color, add = TRUE,
lines.args = list(lwd = 3, lty = 2))
## Example 2: FUN may return more than one value (here: 3)
plot (aggregate (spc, by, mean_pm_sd), "spc",
col = rep(color, each = 3), lines.args = list(lwd = 3, lty = 2))
## Example 3: aggregate even takes FUN that return different numbers of
## values for different groups
plot (spc, "spc", col = color[by])
weird.function <- function (x){
if (length (x) == 1)
x + 1 : 10
else if (length (x) == 2)
NULL
else
x [1]
}
agg <- aggregate (spc, by, weird.function)
agg$.aggregate
plot (agg, "spc", add = TRUE, col = color[agg$.aggregate],
lines.args = list (lwd = 3, lty = 2))