In this part of my series Implementing Technical Indicators I provide you with the R implementation of another technical indicator. Please refer to my article Technical Indicators: An Introduction for an overview of the concept of technical indicators and for details on the particular one presented in this article.

DISCLAIMER: None of the below is intended to be considered as any kind of investment advice. All examples serve as illustrative material only.

For an implementation of the average directional movement index (ADX) please see the R code below. The function `ADX`

calculates the indicator values, which may afterwards be plotted with help of the function `plotADX`

. Note that both function use tools introduced in my article Implementing Technical Indicators: Tools.

```
#
# AVERAGE DIRECTIONAL MOVEMENT INDEX
#
source("Indicators/IndicatorHelperFunctions.R")
source("Indicators/IndicatorPlottingFunctions.R")
source("Indicators/ATR.R")
# indicator calculation
ADX = function(v_high, v_low, v_close, i_window=10)
{
checkVectors(v_high, v_low, v_close)
checkWindow(v_close, i_window)
i_length = length(v_close)
# directional movement
v_high_diff = c(0, (v_high[2:i_length] - v_high[1:(i_length-1)]))
v_low_diff = c(0, (v_low[1:(i_length-1)] - v_low[2:i_length]))
v_mDM = rep(0, i_length)
v_pDM = rep(0, i_length)
v_mDM[(v_low_diff > v_high_diff)] = pmax(0, v_low_diff[(v_low_diff > v_high_diff)])
v_pDM[(v_high_diff > v_low_diff)] = pmax(0, v_high_diff[(v_high_diff > v_low_diff)])
# directional index
v_mADM = movingAverage(v_mDM, i_window)
v_pADM = movingAverage(v_pDM, i_window)
v_atr = ATR(v_high, v_low, v_close, i_window)$ATR
v_mDI = 100 * v_mADM / v_atr
v_pDI = 100 * v_pADM / v_atr
# ADX
v_dx = abs((v_pDI - v_mDI) / (v_pDI + v_mDI))
v_dx[is.na(v_dx)] = 0
v_adx = 100 * movingAverage(v_dx, i_window)
df_adx = data.frame(v_adx, v_mDI, v_pDI, v_close)
colnames(df_adx) = c("ADX", "mDI", "pDI", "Close")
return(df_adx)
}
# indicator plotting
plotADX = function(v_date, df_adx, s_path)
{
isDataFrame(df_adx)
dateMatch(v_date, df_adx)
v_colors = c("black", "blue")
v_legend = c("ADX", "Close")
plotIndicator2(v_date, df_adx$ADX, as.data.frame(df_adx[, 4]), v_colors, v_legend, s_path)
}
```