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R package of similarity tool methods for use in comparing players batted ball and offensive peripheral profiles
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README.md

similarityTool

R package of similarity tool methods for use in comparing players batted ball and offensive peripheral profiles

What is this?

This package is designed to generate comparisons for a given player based on their batted ball or offensive profile using FanGraphs data.

How does it work?

Please see here: https://www.fangraphs.com/community/an-exercise-in-generating-similarity-scores/. My methodology is explained and discussed fairly in-depth in that article, but I'm also more than happy to answer any questions you have - scroll down for my contact info.

What does BB or Off mean?

BB refers to batted ball profile. For functions with the "BB" tag, the similarity scores are based solely upon batted ball data from FanGraphs, specifically the following metrics: LD%, FB%, GB%, HR/FB, Pull%, Cent%, Oppo%, Soft%, Med%, Hard%.

Off refers to offensive peripherals - this includes all of the metrics in BB but with BB% and K% included as well.

How do I use it?

Get R and Rstudio installed (obviously), then import devtools and load them.

> install.packages("devtools")
> library("devtools")

Then, install the package from this github directory, and load them into Rstudio.

> install_github('Metlover/similarityTool')
> library('similarityTool')

You now have all the packages you need loaded onto your computer.

Next, you need the data from FanGraphs. For 2017 batted ball data of qualified batters across the MLB, for instance, go here: (http://www.fangraphs.com/leaders.aspx?pos=all&stats=bat&lg=all&qual=y&type=2&season=2017&month=0&season1=2017&ind=1&team=0&rost=0&age=0&filter=&players=0)

You must have "Split Seasons" selected, even if only using the data from a single season. Otherwise, this function will not work properly.

If using only batted ball functions, simply click "Export data" in the upper right corner of the table.

If using Off functions, scroll down to the bottom of the screen below the table. In the list on the far left, scroll down and select "BB%", then click on the "To Right" arrow. Repeat this for "K%". Then click on "create custom table", and then click on "Export data".

If using Pitching functions, select "BB/9" and "K/9" instead of "BB%" and "K%".

Please note that datasheets with batted ball data and K% and BB% are compatible with both Off and BB. If you are missing BB% and K% data, Off functions will not work. Pitching functions require "K/9" and "BB/9" to work properly.

In both cases, you should end up with a CSV of either BB or Off data. Import the CSV as a dataset by going from File -> Import Dataset -> From Text (readr)... and select the CSV of the batted ball data. Feel free to name it something simple like "battedBallData".

From there, use the functions to obtain similarity scores from the dataset. For example, the following command yeilds the most similar players based on offensive peripherals to Nolan Arenado in 2017 among qualified hitters:

> result <- similarityToolOff(battedBallData, "Nolan Arenado", 5, 2017)
Warning message:
package ‘FNN’ was built under R version 3.4.2 
> result
               Name   Scores
1       Ian Kinsler 1.228740
2      Justin Smoak 2.106559
3 Andrew Benintendi 2.191174
4  Francisco Lindor 2.320362
5    Mike Moustakas 2.459700

Check the documentation, the forthcoming FanGraphs article, and below for how to use the other functions.

What does each tool do?

similarityToolBB.R | similarityToolOff.R

This is the most fundamental function. Given batted ball or offensive peripheral data from FanGraphs and the name of a player within the dataset, this function will output the most similar players and their similarity scores.

similarityToolBBx.R | similarityToolOffx.R

This function works similarly to the above function, but takes a singular data frame of batted ball profile as the input instead of a name - i.e., PlayerVals = data.frame("LD%" = .xxx, "GB%" = .xxx, "FB%" = .xxx, "Pull%" = .xxx, "Cent%" = .xxx, "Oppo%" = .xxx, "Soft%" = .xxx, "Med%" = .xxx, "Hard%" = .xxx, "HR/FB" = .xxx, check.names=FALSE) (include BB% and K% for the offensive metric).

similarityToolMostSimBB.R | similarityToolMostSimOff.R

This function relies upon similarityToolBB/Off.R to find players with the lowest overall similarity scores, i.e. what players are most similar to other players within a dataset.

similarityToolMostUniqueBB.R | similarityToolMostUniqueOff.R

Acts in reverse of the MostSimBB/Off and finds the players with the highest overall similarity scores, i.e. what players are most unique.

similarityToolTwoPlayersBB.R | similarityToolTwoPlayersOff.R

Finds the similarity score between two players. NOTE THAT THIS REQUIRES A FULL DATASET - because of the normalization techniques used in similarityToolBB/Off, an accurate similarity score will not be generated if the dataset consists only of the two players.

Hey, it broke! What did I do wrong?

I have not implemented any kind of error-catching and whatnot yet, though I may get around to it. If you encounter some kind of error, feel free to tweet @ me on twitter with your error (@John_Edwards_)_ and I will do my best to resolve the issue. This whole project was done in my spare time over the course of a few days, so I do not expect it to be perfect.

Have you considered doing X?

No, I probably haven't! I'm an R noob and this is my first big project in R, and I'm sure that there's some mistakes that I've made, or done something inefficiently, etc. etc. If you have any suggestions for the project, be it bug fixes, new features, optimization, etc., again, @ me on twiter (@John_Edwards_)_ and I will see what I can do.

Future Changes

  • Functionality to compare players across multiple seasons done as of 12/17/17
  • Pitcher comparisons (coming soon) also done as of 12/17/17
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