[R] Clustering function

[N. Goodacre]

Dear mailing group,

  I have loaded an Excel file into R by calling it ".csv" and using the 
"read.csv" function in R. However then I want to use the (limma package 
specific, I believe) function "hclust", which clusters data in a tree 
dendrogram, by similarity. However, I receive the errors msg.s: 1) "missing 
observations in cov/cor" 2) "In addition: warning message: NAs introduced 
by coercion"

The excel file does have missing data slots. Do these tow messages mean 
that it has written "NA" where the missing slots were? Or is there a more 
fundamental error?

 thanks.

-Norman