I too don't understand the error message.  However Coefficient Alpha is 
easily calculated. To wit:

library("psych")
tt <- cbind(c(1,0.58) , c(0.58,1))
colnames(tt) = rownames(tt) = list("V1" , "V2")

p <- nrow(tt)
alpha <- p/(p-1) * (1-sum(diag(tt))/sum(tt))


Numerous caveats regarding using C-Alpha apply.  And because you have the 
factor loading you have the reliability of the factor.  You don't need 
C-Alpha.





Johannes Moser <joh.mo@web.de> 
Sent by: r-help-bounces@r-project.org
02/14/2014 05:24 PM

To
r-help@r-project.org, 
cc

Subject
[R] psych package - Cronbach`s Alpha -  warning message






Dear R-help,

I try to estimate alpha for a factor that loads onto two items, using 
the psych-package (newest version).
The data is from the boston housing data set.

The problem I face can be reproduced by the following approximation of 
the correlation matrix:

library("psych")
tt <- cbind(c(1,0.58) , c(0.58,1))
colnames(tt) = rownames(tt) = list("V1" , "V2")
alpha(tt)


R Version 3.0.2 (2013-09-25) 64 Bit  -  Platform: Windows 7 
Professional, 64 bit
I have tried on two different Windows computers - same warning messages:

In matrix(unlist(drop.item), ncol = 6, byrow = TRUE) : data length [10] 
is not a sub-multiple or multiple of the number of columns [6]

What is the reason for the warning?
Is it to be taken seriously?
How can I avoid this warning?

I would be very thankful for any ideas or advice!
Thank you a lot in advance!!!





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