Plotting Statcast data

In this example, the baseballr package is used to acquire Statcast data for Mookie Betts from 2015-2016.

The data is then processed and plotted to show how his launch angle and batted ball speed have changed from year to year

library(baseballr)
library(dplyr)
library(ggplot2)
library(reshape2)
library(zoo)

find Mookie Betts’ MLBAMID

betts_id <- playerid_lookup("Betts") %>%
  dplyr::filter(first_name == "Mookie") %>%
  dplyr::select(mlbam_id, first_name, last_name)

scrape Betts’ Statcast data, by pitch removing those with a batted ball speed of 0

betts_15 <- statcast_search("2015-03-31", "2015-10-31", playerid = betts_id[1,1], player_type = 'batter')
betts_16 <- statcast_search("2016-03-31", "2016-10-31", playerid = betts_id[1,1], player_type = 'batter')   
betts <- dplyr::bind_rows(betts_15, betts_16) %>%
  dplyr::mutate(Year = as.factor(substr(game_date,1,4))) %>%
  dplyr::filter(type == "X") %>%
  dplyr::filter(launch_speed != 0)

calculate average launch angles and batted ball speeds by game

betts_grpd <- betts %>%
  dplyr::group_by(game_date) %>%
  dplyr::summarise(
    `Average Launch Angle` = mean(launch_angle, na.rm = TRUE), 
    `Average Batted Ball Speed` = mean(launch_speed, na.rm = TRUE)) %>%
  dplyr::ungroup() %>%
  melt(id=c("game_date")) %>%
  dplyr::mutate(Year = as.factor(substr(game_date,1,4)))

calculate Betts’ average launch angle and batted ball speed by year

betts_avg_speed_yr <- betts %>%
  dplyr::group_by(Year) %>%
  dplyr::summarise(
    speed = round(mean(launch_speed, na.rm = TRUE),1), 
    angle = round(mean(launch_angle, na.rm = TRUE),1))

plot the data

betts_grpd %>%
  ggplot(aes(game_date, value)) +
  geom_point() +
  stat_smooth(aes(group = Year, color = Year)) +
  facet_wrap(~variable, scales = "free_y") + 
  ggtitle("\nMookie Betts: 2015 vs. 2016\n") + 
  labs(subtitle = paste0("Betts has lowered his launch angle in 2016, from ", betts_avg_speed_yr[1,3], " degrees in 2015 to ", betts_avg_speed_yr[2,3], " degrees this year.\n\n"), 
       caption = "@BillPetti\nData from baseballsavant.mlb.com\nData acquired with the baseballr package") +
  ylab("Angle = Degrees, Speed = MPH\n") +
  xlab("\nDate") +
  #theme_bp_grey() + 
  theme(legend.position = "bottom", strip.text.x = element_text(face = "bold", size = 14), plot.subtitle = element_text(hjust=-.12)) +
  scale_color_manual(values = c("#5F9ED1", "#FF800E"))

Uncomment and run to export plot to your working directory

# ggsave("betts_angle_speed_year.png", scale = 1.2, width = 14, height = 8.5, units = "in")