# R for Psychological Research, Lesson 7: Summarise groups
# Code from the lesson page, in order. Run it line by line with Ctrl+Enter (Cmd+Enter on a Mac).
# Lines that start with # are comments: R ignores them.


# ---- Set up ----

library(tidyverse)
students <- read_csv("data/students.csv", show_col_types = FALSE)


# ---- summarise(): many rows to one ----

students %>%
  summarise(n = n(), mean_exam = mean(ExamScore), sd_exam = sd(ExamScore))


# ---- group_by(): one summary per group ----

students %>%
  group_by(Motivation) %>%
  summarise(n = n(),
            mean_exam = mean(ExamScore),
            mean_study = mean(StudyHours, na.rm = TRUE))


# ---- Put groups in order ----

students <- students %>%
  mutate(Motivation = factor(Motivation, levels = c("Low", "Medium", "High")))

students %>%
  group_by(Motivation) %>%
  summarise(n = n(), mean_exam = mean(ExamScore))


# ---- Two groupings at once ----

students %>%
  group_by(Workshop, Gender) %>%
  summarise(n = n(), mean_change = mean(Wellbeing_T2 - Wellbeing_T1), .groups = "drop")