How to prevent a data frame degrading to a vector

Post date: Apr 2, 2014 8:26:44 AM

Normally a dataframe is supposed to have more than 1 column. By default when n-1 columns are dropped from an n-column data frame, the remaining 1 column will be automatically degraded to a vector. To prevent such degradation, use 'drop=F' when subsetting the data frame. For example:

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