function [y,no] = f1(x,ni)

x = x(:);
np = length(x);
if length(x) ~= length(ni)
    disp 'error: vectors not same length'
    return
end

h = (0.9).^[0:10];
y = conv(x,h);
no = [min(ni):max(ni)-1+length(h)];
