[R] Receiving NaN message

Hello, I am working on a Coursera assignment and have combined 332 files into a single data frame called "dat". The dataframe has 4 columns, 1. Date 2. Sulfate (numerical values) 3. Nitrate (numerical values) 4. ID # (numerical values). Our assignment is to write a function pollutantmean <- fu

[R] Test

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