How to only consider data after a series of time points

I have a Force x Time graph, and I am trying to write a code to determine the time point when the Force drops below 0, on the condition that it has already decreased past threshold 1 value, then increased past threshold 2 value, then decreased past threshold 3 value. How can I ensure these criteria have been met before i look for my first 0 value using

F1 = find(F < 0.001, 1, 'first')

Thanks in advance

Answer 1

[Ridwan Alam]

If I understood it right, you have threshold values T0(=0?),T1,T2,T3:

F0 = find(F(2:end)<T0 & F(1:end-1)>=T0) +1; % indices of F decreasing past T0
F1 = find(F(2:end)<T1 & F(1:end-1)>=T1) +1; % indices of F decreasing past T1
F2 = find(F(2:end)>=T2 & F(1:end-1)<T2) +1; % indices of F increasing above T2
F3 = find(F(2:end)<T3 & F(1:end-1)>=T3) +1; % indices of F decreasing past T3

if ~isempty(F1)
    tempF2 = F2(F2>F1(1));
    if ~isempty(tempF2)
        tempF3 = F3(F3>tempF2(1));
        if ~isempty(tempF3)
            finalIndex = F0(find(F0>tempF3(1),1,'first'));
        end
    end
end

Hope it helps!

[Ridwan Alam]

BW = mean(F(4000:5000))
T1 = BW*0.9
T2 = BW*1.2
T3 = BW*0.9
T0 = 0

% BW =
%   774.3022
% T1 =
%   696.8720
% T2 =
%   929.1626
% T3 =
%   696.8720

F0 = find(F(2:end)<T0 & F(1:end-1)>=T0) +1; % indices of F decreasing past T0
F1 = find(F(2:end)<T1 & F(1:end-1)>=T1) +1; % indices of F decreasing past T1
F2 = find(F(2:end)>=T2 & F(1:end-1)<T2) +1; % indices of F increasing above T2
F3 = find(F(2:end)<T3 & F(1:end-1)>=T3) +1; % indices of F decreasing past T3
if ~isempty(F1)
    tempF2 = F2(F2>F1(1));
    if ~isempty(tempF2)
        tempF3 = F3(F3>tempF2(1));
        if ~isempty(tempF3)
            finalIndex = F0(find(F0>tempF3(1),1,'first'));
        end
    end
end

% finalIndex =
%         7372