Correlation matrix is not positive definite about bootnet

[SachaEpskamp]

While the original sample has 43 cases, the bootstrapped samples will have fewer than 43 cases leading to potentially non-positive definite correlation matrices used as input. While technically EBICglasso can still be used (you would have to overwrite this error both in qgraph and bootnet) I really do not advice you to do so. See here for more info:

#126

[stonelight816]

Hi Sacha,

thanks for your response. In this example:#126, the number of datapoints was fewer than number of nodes. In my project, number of datapoints (43) beyonds the number of nodes (37). Why would this error still happened?

[SachaEpskamp]

Even though you have more datapoints than nodes in the original data, you don't have this in the bootstrapped data as you resample cases with replacement, leading to less unique cases. See for example:

# Original data with N = 11; P = 10:
data <- matrix(rnorm(11*10),11,10)
all(eigen(cor(data))$values > 0)
# Is positive definite

# Bootstrap sample:
set.seed(42)
bootdata <- data[sample(1:nrow(data),nrow(data),TRUE),]
all(eigen(cor(bootdata))$values > 0)
# No longer positive definite