Hello, I was wondering if someone might be able to help me with some coding issues. I know how to make a generic boxplot using the appropriate data but I was wondering if there was a way to distinguish between categorical variables within another categorical variable on boxplots. For example: my data set has the variables- Trial#, Site, Treatment_Salinity as my various categorical variables. I am wanting to create boxplots comparing Time Trial Data for each site (two different sites), trial#(three different trials) and salinity treatments (7 per site per trial). As of right now I was able to get the boxplots to compare just the salinity time trial differences but I need to be able to compare with those three variables essentially stacking into one another (I am sorry if this is confusing).

Another issue I am having is that right now I have a "." in the place where there is no data available for the numerical data, should I change that to NA so that R excludes it or should I leave the excel cell empty? 0's are values I have for the time trial data so I can't use 0 as a placeholder.

With the boxplots, is it possible to exclude anything that has 3 or less replicates? I realize this is a lot of questions but I am really struggling with this. Any and all help is appreciated.

Thank you!