Directional Movement Index - ADX Slope

study(title="Directional Movement Index - ADX Slope", shorttitle="ADX-SLOPE")
len    = input(14, title="DI Length",     minval=1)
lensig = input(14, title="ADX Smoothing", minval=1, maxval=50)
lenslp = input(1,  title="Slope Length",  minval=1)

up   = change(high)
down = -change(low)
trur = rma(tr, len)
plus = fixnan(100 * rma(up > down and up > 0 ? up : 0, len) / trur)
minus = fixnan(100 * rma(down > up and down > 0 ? down : 0, len) / trur)
sum = plus + minus 
adx = 100 * rma(abs(plus - minus) / (sum == 0 ? 1 : sum), lensig)

slope = (adx - adx[lenslp])/lenslp

hline(0,    color=gray,  title="Zero")
plot(slope, color=black, title="ADX Slope", style=histogram)