Hello,
I would like to please ask if someone would explain how r reads characters
and numbers differently.  Using read.csv, I had a matrix that resembled the
following, only with many more ids and data:

    ID
 Visit
 variable
 2
 1
 5
 2
 1
 3
 2
 3
 4
 2
 41
 1
 2
 42
 34
 2
 5
 54
 2
 9
 1
 2
 10
 3
 2
 12
 5
 5
 1
 54
 5
 2
 9
 5
 3
 3
 5
 41
 54
 5
 41
 2
 5
 5
 235
 5
 9
 4
 5
 10
 2
 5
 12
 2

I then tried to subset for Visit==3.  However, subset == was not working
properly.  This gave me zero rows.  I printed the matrix/dataframe and
found that this was because r viewed the 3 as " 3" (space three).  So, I
had to type subset == " 3" to select for the data instead.  I think this
has to do with character, number and string properties, but I am quite a
novice.  Would anyone be able to instruct me how one tells a
dafaframe/matrix to convert numbers such as " 3" to "3" so that I do not
get confused in the future?  I guess another problem I have is that I am
still learning the differences between matrices and dataframes.
Thanks so much, Matt

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