function [Amp, Latency] = ave_peakA(MData,sign,t1,t2,pre)
% finds positive or negative peak for each epoch.
% if sign is 1, find the positive peak. if sign is -1, finds negative peak.
MeanData = sign*MData;
[Amp, Latency] = peak(MeanData,t1,t2,pre);
end