dplyr-adv-nulls.md

Maybe do this material in conditionals?

Handling nulls (more generally)

• To remove only rows with NA in specific columns use filter

filter(surveys_by_species, weight != NA)

• Why didn't that work?
• Null values like NA are special
• We don't want to accidentally say that two "missing" things are the same
  • We don't know if they are
• So use special commands
• is.na() checks if the value is NA
• Combine this with ! for "not"

filter(surveys_by_species, !is.na(weight))

• So !is.na(weight) is conceptually the same as "weight != NA"

surveys_by_species_nonull <- filter(surveys_by_species,
                                    !is.na(weight))
species_weight <- summarize(surveys_by_species_nonull,
                            avg_weight = mean(weight))

Do [Portal Data Manipulation 4-6]({{ site.baseurl }}/exercises/Portal-data-manip-R/).