This function uses the user-defined 'period of analysis', and subsets the Daily data frame, it doesn't have any effect on the Sample data frame. If you want to examine your data set as a time series of water years, then the period of analysis is October through September. If you want to examine the data set as calendar years then the period of analysis is January through December. You might want to examine the winter season, which you could define as December through February, then those 3 months become the period of analysis. The only constraints on the definition of a period of analysis are these: it must be defined in terms of whole months; it must be a set of contiguous months (like March-April-May), and have a length that is no less than 1 month and no more than 12 months. Define the PA by using two arguments: paLong and paStart. paLong is the length of the period of analysis, and paStart is the starting month.

`selectDays(df, paLong, paStart)`

localDaily a data frame containing the daily data but only for the period of analysis (not all months)

- df
dataframe which must contain a column named Month (for month of the calendar year, typically this is a Daily data frame.

- paLong
a numeric value for the length of the period of analysis, must be an integer from 1 to 12

- paStart
a numeric value for the starting month of the period of analysis, must be an integer from 1 to 12

```
eList <- Choptank_eList
Daily <- getDaily(eList)
DailySubset <- selectDays(Daily, 4, 11)
```

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