MikeTP questions

• How to use ggplot to group and show top X categories?
• read.csv appends/modifies column headings with date values
• linear model when all occurrences of independent variables are NA
• Read list of file names from web into R
• ggplot2 scale_x_continuous limits or absolute
• How can I make geom_boxplot outliers "line up" with jittered geom_points?
• Beginner tips on using plyr to calculate year-over-year change across groups
• Add image (png file) to header of pdf file created with R
• removing trailing spaces with gsub in R [duplicate]
• Subset R data frame contingent on the value of duplicate variables

MikeTP answers