[amibroker] Is there an AFL function that automatically returns yesterday's value?

["l_abarr" <l_abarr@xxxxxxxxx>]

I'm new at this. I want UpVol to remain the same as yesterday if there
is a down day (C < O). In other words, I don't want a zero UpVol value
if there's a down day: I'd prefer for UpVol to remain at the previous
day's value. Same for DownVol: I don't want a zero value if there's an
up day: just want today's value to remain at yesterday's value. 

Thanks!

UpVol =IIf(C > O, V, YESTERDAY'S UpVol VALUE);
DownVol =IIf(C < O, V, YESTERDAY'S DownVol VALUE);
Period = Param("Period",3,2,10,1);
UpVolAvg = EMA( UpVol, Period ) ;
DownVolAvg = EMA( DownVol, Period ) ;
Plot(UpVolAvg,"UpVolume", colorGreen);
Plot(DownVolAvg, "DownVolume", colorRed);



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