# NMF - Subscript out of bounds

I've calculated the cophenetic coefficients for the NMF of gene expression data, but is giving error when performing the clustering information step as given below:

clustered_data <- NMF_estimate[[num.opt - 1]][[2]]


Error in NMF_estimate[[num.opt - 1]] : subscript out of bounds

Here num.opt is num.opt <- coph[which(coph[,2]==max(coph[-1,2])),1] which gives 2, 5 as outputs, and NMF Estimate is a list of 6 elements.

Please suggest a solution as soon as possible.