Fitbit Surge vs. Polar H7 + Nexus 6 + Strava: Comparing Heart Rate Sensors

heartRateComparison.r

library(XML)
library(dplyr)
library(lubridate)
library(reshape2)
library(ggplot2)

fitbit <- xmlToDataFrame(getNodeSet(xmlParse("fitbit.tcx"), "//ns:Trackpoint", "ns"),
  stringsAsFactors = FALSE)

strava <- xmlToDataFrame(getNodeSet(xmlParse("strava.tcx"), "//ns:Trackpoint", "ns"),
  stringsAsFactors = FALSE)

  
fitbitG <- fitbit %>%
  mutate(
    Time = as.POSIXct(strptime(Time, "%Y-%m-%dT%H:%M:%S")),
    HeartRateBpm = as.numeric(HeartRateBpm)
  ) %>%
  select(Time, HeartRateBpm)
  
stravaG <- strava %>%
  mutate(
    Time = as.POSIXct(strptime(Time, "%Y-%m-%dT%H:%M:%SZ") - hours(7)),
    HeartRateBpm = as.numeric(HeartRateBpm)
  ) %>%
  select(Time, HeartRateBpm) %>%
  filter(Time >= as.POSIXct("2016-08-14 17:38:10"))

both <- full_join(fitbitG, stravaG, by = c("Time")) %>%
  rename(
    "Fitbit Surge" = HeartRateBpm.x,
    "Strava + Nexus 6 + H7" = HeartRateBpm.y)
both %>%
  na.omit() %>%
  transmute(diff = .[[2]] - .[[3]]) %>%
  summarise(averageDifference = mean(diff))

longData <- melt(both, id.vars = "Time") %>%
  na.omit()

ggplot(longData, aes(Time, value, color = variable)) +
  geom_line() +
  coord_cartesian(ylim = c(120, 190)) +
  labs(title = "Comparing Heart Rate Sensor Readings") +
  theme(legend.position = "bottom")