Importing Excel format data into R/R Studio and using glmnet package? I have no problem importing Excel formatted data into R/R Studio and use all other R packages that I use.  But, when I want to use the glmnet package to develop a regularization model, I invariably run into the following error (after specifying my regularization model and attempting to run it): 

Error in storage.mode(y) &lt;- "double":
  (list) object cannot be coerced to type 'double'


Here is what I have already tried to resolve this:


De-format the numbers in Excel (no scientific notation, no %, etc.)
Did copy-paste-special values several times
At time of importing the spreadsheet, converted every column from "include" to "numeric" type
After importing the data, converting it to a matrix. 


But, none of the above have eliminated the error.
After soliciting assistance from many colleagues, I found the answer to my problem.  And, I thought it be worth sharing.  glmnet package requires that you format your data as matrix.  

What I had already done is import and transform the data as matrix as follows:

data.matrix(data)


But, that is not enough.  You still have to convert the X and Y arrays as matrix as follows:

a) First do the x matrix: 
x = as.matrix(data,...);
b) Second do the y matrix: y = as.matrix(data,...). 

Once I did the above change the glmnet package seems to work just fine.

I am unclear why the glmnet package is so much more sensitive to how much you matricize your data.  But, that is the way it is.