B. Davis questions

• Preserving many columns when using gather
• Adding missing date values in a data frame with multiple observation periods
• Converting Date/Time stamp into correct R Format using chron()
• Double box plots in ggplot2
• Plotting rectangles in ggplot2 - Invalid input: time_trans works with objects of class POSIXct only
• Remove the first N rows from each factor level in an r data.frame
• Legend in ggplot when aes() color and shape are not specified
• Fill in gaps (e.g. not single cells) of NA values in raster using a neighborhood analysis
• Extract items from a list using get() and paste() in R
• summary statistics of multiple data frames within a list

B. Davis answers