euler | R Documentation |
Mostly an for internal use in conjunction with resels
. Calculates the
euler characteristic at a threshold level.
euler(u, df, fieldType)
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 |
|
A vector of estimated euler characteristics for dimensions 0:D
Zachary P. Christensen
Worlsey K.J., (1996) A Unified Statistical Approach for Determining Significant Signals in Images of Cerebral Activation.
rftPval, resels
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)
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