euler: Euler Character

In stnava/ANTsR: ANTs in R: Quantification Tools for Biomedical Images

Euler Character

Description

Mostly an for internal use in conjunction with resels. Calculates the euler characteristic at a threshold level.

Usage

euler(u, df, fieldType)

Arguments

u	statistical value (typically the maxima of a cluster or statistical field)
df	degrees of freedom expressed as df = c(degrees of interest, degrees of error)
fieldType	T: T-field F: F-field X: Chi-square field' Z: Gaussian field

Value

A vector of estimated euler characteristics for dimensions 0:D

Author(s)

Zachary P. Christensen

References

Worlsey K.J., (1996) A Unified Statistical Approach for Determining Significant Signals in Images of Cerebral Activation.

See Also

rftPval, resels

Examples

mask <- getMask(antsImageRead(getANTsRData("r16")))
myresels <- resels(mask, c(1, 1))
# pretend these results are from a t-statistical field fitted with 10 df to
# find a peak value.
df <- c(1, 10) # made up degrees of freedom
ec <- euler(4, df, fieldType = "T") # peak value is 4
ez <- euler(3, df, fieldType = "T") # we thresholded at 3
# uncorrected peak-level p-value
pvox <- sum(ec * myresels) / sum(ez * myresels)

stnava/ANTsR documentation built on Sept. 19, 2024, 12:02 a.m.