[amibroker] Use set previous period

["lamplowman" <lamplowman@xxxxxxxxxxxx>]

I've made a graph

Plot (Close,"Close",1,64);

xyz = L + (ATR(14) * 2);
zxy = H - (ATR(14) * 2);
Plot (xyz,"myhigh",3,1);
Plot (zxy,"mylow",4,1);

def1 = Lowest(xyz);
Plot (def1,"def1",3,1);

def2 = Highest(zxy);
Plot (def2,"def1",4,1);

How can I get this graph to cover only a certain period of time.
ie, I only want it to start about 3 weeks ago.

I'm new to AB and not familiar with the commands and can't find it
searching the help file for probable words.

Peter





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