I have 
    a simple script that calculates the correlation between two instruments. I 
    then take the code we've been discussing for historical volatility, and try 
    to plot the volatility of the correlation. However the second plot function 
    of the volatility just shows a flat line at 0. Any ideas what I'm missing 
    here?
    t1 = Correlation( Foreign(instrument1, 
    "Close"), Foreign(instrument2, "Close"), 
    period1);
    Plot(t1, "Correlation", 
    colorYellow);
    hv1 = 
    StDev(log(t1/Ref(t1,-1)),period1)*sqrt(260);
    
    Plot(hv1,"Volatility", 
    colorWhite,styleLine|styleOwnScale);