I have a data matrix that contains names of samples as columns and lists of genes as rows. After transposing the matrix and calculating the z-scores using the scale() function, I transposed my matrix back. 
Now I'm interested in subsetting my dataframe. So for example, if Sample 1 has rows that have values 2 standard deviations away from the mean, I would like to extract that rows and store it in a variable.
I've tried to select() my data frame however I'm getting this error message: 
Error in (function (classes, fdef, mtable) : unable to find an inherited method for function ‘select’ for signature ‘"matrix"
Additionally after transposing the matrix back, I'm unable to get column names.
I have also used the abs() function however it returns a TRUE and FALSE values, however I still get the same error message if I try to select columns based on if they are TRUE or not 
Any help would be really appreciated
