Exercise_PowerCalc_5.3.2021.Rmd

# 5.3.2020
# This script calculates power for observing effects of exercise!

# thuyvy's power function:
```{r}
gotta_power = function(data, trait, power_per) {
  #'@param trait - ECG trait
  #'@param power_per - power, as a decimal
  ptab <- cbind(NULL, NULL)
  for (i in seq(from = 0.02, to = 1, by = 0.02)) {
    pwrt <-
      power.t.test(
        delta = ((mean(data[,trait])*i)+mean(data[,trait]))-mean(data[,trait]),
        sd = sd(data[,trait]),
        power = power_per,
        type = "two.sample",
        alternative = "two.sided"
      )
    ptab <- rbind(ptab, cbind(pwrt$delta, pwrt$n, i*100))
  }
  power_table = as.data.frame(ptab)
  names(power_table) = c("delta", "n", "percent")
  power_table<<-power_table
}
```

# read data
```{r}
df = readRDS('/Volumes/JHPCE 2/dcs01/active/projects/SHAPE/R_objects/final_shape35_dataset.rds')
noNA = df[-which(is.na(df$mtDNA_change)),]
gotta_power(noNA, 'mtDNA_change', 0.8)

power.t.test(
        n = nrow(noNA),
        sd = sd(noNA$mtDNA_change),
        power = 0.8,
        type = "two.sample",
        alternative = "two.sided"
      )
```