W2 Self-Test
Wenling Zhao
16 June, 2026
Welcome to the PSYC3361 coding W2 self test. The test assesses your ability to use the coding skills covered in the Week 2 online coding modules.
In particular, it assesses your ability to…
- choose packages/functions
- read in data
- make a scatter plot
- use facet_wrap
- customise your plot with themes, colours and labels
- use group_by and summarise
It is IMPORTANT to document the code that you write so that someone who is looking at your code can understand what it is doing. Above each chunk, write a few sentences outlining which packages/functions you have chosen to use and what the function is doing to your data. Where relevant, also write a sentence that interprets the output of your code.
Your notes should also document the troubleshooting process you went through to arrive at the code that worked.
For each of the challenges below, the documentation is JUST AS IMPORTANT as the code.
Good luck!!
Jenny
PS- if you get stuck have a look in the /images folder for inspiration
Load the packages you need
library(tidyverse)Read in the dino data
dino_data <- read_csv("data/dino.csv")
print(dino_data)## # A tibble: 1,846 × 3
## dataset x y
## <chr> <dbl> <dbl>
## 1 dino 55.4 97.2
## 2 dino 51.5 96.0
## 3 dino 46.2 94.5
## 4 dino 42.8 91.4
## 5 dino 40.8 88.3
## 6 dino 38.7 84.9
## 7 dino 35.6 79.9
## 8 dino 33.1 77.6
## 9 dino 29.0 74.5
## 10 dino 26.2 71.4
## # ℹ 1,836 more rowsreproduce this plot
The dino dataset comes from a paper illustrating the importance of plotting your data. In each of these datasets, the mean and variance of x and y are identical and the two variables are correlated in the same way (R = -0.06). When plotted, however, each reveals a very different pattern
dino_data %>%
ggplot(data = dino_data, mapping = aes(x,y)) + geom_point() + facet_wrap(~dataset) + geom_smooth(method = "lm")## `geom_smooth()` using formula = 'y ~ x'
what can you do to make it prettier
HINT: add some colour, play with palettes, try a different theme, add a title, subtitle, caption
dino_data %>%
ggplot(data = dino_data, mapping = aes(x,y)) + geom_point(colour="blue") + facet_wrap(~dataset) + geom_smooth(method = "lm", color = "purple") + labs(title = "Plots", caption = "haha trinity")## `geom_smooth()` using formula = 'y ~ x'
extra challenge
Can you write code to show that the mean, variance, and correlation between x and y is the same for each of the datasets?? HINT: this is a group_by and summarise problem
dino_data %>%
group_by(dataset) %>%
summarise(meanx = mean(x), meany = mean(y),
varx = var(x), vary = var(y), cor_xy = cor(x, y))## # A tibble: 13 × 6
## dataset meanx meany varx vary cor_xy
## <chr> <dbl> <dbl> <dbl> <dbl> <dbl>
## 1 away 54.3 47.8 281. 726. -0.0641
## 2 bullseye 54.3 47.8 281. 726. -0.0686
## 3 circle 54.3 47.8 281. 725. -0.0683
## 4 dino 54.3 47.8 281. 726. -0.0645
## 5 dots 54.3 47.8 281. 725. -0.0603
## 6 h_lines 54.3 47.8 281. 726. -0.0617
## 7 high_lines 54.3 47.8 281. 726. -0.0685
## 8 slant_down 54.3 47.8 281. 726. -0.0690
## 9 slant_up 54.3 47.8 281. 726. -0.0686
## 10 star 54.3 47.8 281. 725. -0.0630
## 11 v_lines 54.3 47.8 281. 726. -0.0694
## 12 wide_lines 54.3 47.8 281. 726. -0.0666
## 13 x_shape 54.3 47.8 281. 725. -0.0656