# Plotting Statcast data

#### Bill Petti

#### 2023-03-20

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")