This function is generic (see Methods); method functions can be written to handle specific classes of data. Classes which already have methods for this function include:

crystal.matrix.

stretch(x, ...)
stretch.default(x, power.stretch=0, stretch.fun=NULL)
stretch.crystal.matrix(x, low.pass=T, power.stretch=0, stretch.fun=NULL)

x:

a numeric vector or matrix or an object inheriting from class crystal.matrix.

power.stretch:

a numeric value giving the power of the transform if stretch.image is TRUE. If power.stretch=0, then image is transformed with log(abs(x)+1). Otherwise, the image is transformed with (abs(x))^power.stretch.

stretch.fun:

the image will be transformed using stretch.fun. If provided, then power.stretch will be ignored.

low.pass:

logical flag, if TRUE the smooth/low-frequency coefficients are scaled to have the same dynamic range as the remaining coefficients. Only for objects which inherit from class wpt.2d (2-D DWT and 2-D wavelet packet transforms).