Homework 04 Ready for Grading

[NSKrstic]

You can find my code (and my reflections within the same markdown document) here:

https://github.com/NSKrstic/STAT545-hw-Krstic-Nikolas/tree/master/hw04

[danaj191]

Hey there! Your homework 4 looks great. (The structure of your repo is really well-organized so I didn't have trouble finding your md file for HW 4, but it could've been even a bit easier if you had included a link to it directly in your readme!) You clearly have a great grasp of R and with many of the functions we've been exploring within it. The scatterplots you created from your pairwise combinations were especially interesting, but could have benefitted a bit from some labeling (title and axes).

Really thorough exploration of the different joins for the latter part of the assignment -- nice work. You also described well what each join does. A little bit more description throughout some of the other parts of your assignment (most notably the data reshaping part) also would've been welcome for the reader to follow along, but overall it was still easy to follow what you did and problems you encountered (described during your reflection).

Great job!

[ksedivyhaley]

Reshaping activity: Yes (see comments) Join activity: Partial (see comments) Reflect on process: Yes Bonus (merge/match): Yes

Comments:

• We were expecting you to use gather() and spread(), though dcast() does appear to have a very similar function.
• Taking the mean of life expectancy is unnecessary in the first part, since there is only one life expectancy value per year.
• You also don't need to specify column names in kable.
• You're not able to fully demonstrate the properties of joins unless your left-hand data frame has some countries that are not present in the right-hand data frame. For this exercise, left_join and inner_join should not produce identical results, and semi_join shouldn't just return the same data frame as you feed it.

Your mark will be distributed later. If you would like more feedback, please feel free to message me on slack.

[dorawyy]

Hi Nikolas,

Overall, I feel like you are already an advance user of R already 😃

• I do like your coding style. You made use of variables and assignment to variables, which makes your code readable and easy to follow;
• You tried the wide format data
• You applied dcast() and advanced operations towards vectors( for example, c("Year", names(lifeExp_countries)[2:ncol(lifeExp_countries)] ;
• Your tables are well formatted with the kable();
• You almost finish all activities in the two parts (except making cheatsheet) !

Here is minor suggestion:

• Though it is great to use dcast(), it will be even better to also include gather() and spread() into some activities, as that is the objective of this assignment.
• Moreover, as you applied dcast() for data reshaping as replacement for gather() and spread(), some comparison between {gather(), spread()} and dcast() can be done.

-Yingying