Hi and welcome to your first question. It does not sound at all trivial.
We probably do need to see your code and and some sample data. Generally we need to see the nitty-gritty of both code and data. R can be very picky about things.
Assuming that you have successfully read in the data from the Excel file, You can supply some sample data with the dput() function. In the case of a large dataset something like dput(head(mydata, 100)) should supply the data we need.
Just do dput(mydata) where mydata is your data. Copy the output and paste it here between
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Code should also be pasted between
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to maintain formatting.
Here is a link to some general guidelines :
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