Content and rate of change in a buffer

this is a part of my code

I have a buffer and its content is changing according to the time and rates. I dont want Buffervalue to become zero so I want it to stay zero until the end of the time slot, when its ammount hits 0.

This is my code :

Time=[0.5 1 5 8 10 20 22 39 40 42 50 51 55 60 69 70 73 100 102 110];
Buff=0;
Buffervalue= zeros(1,10);
rate=[1 0.3 -16 2 -16 2 7 -16 -16 0.4 1 0.3 -16 2 -16 2 7 -16 -16 0.4];


for slot= 1:20
    if Buff+(Time(slot)*rate(slot))<=0 
         Buffervalue(slot)=0;
    else

    Buff= Buff+(Time(slot)*rate(slot));
    Buffervalue(slot)=Buff;
    end

end

plot(Time,Buffervalue)

The problem is I have only one negative rate (-16) but when I look at the plot there are different slopes, so it kind of seems wrong to me.

Do you have any idea?

Answer 1

[Mathieu NOE]

hello

IMHO, the non uniform x spacing is prone to bug - so I prefered to resample the data with constant x spacing .

Now I wonder how the rate profile is supposed to evolve between "raw" values given in first place. a linear interpolation is my first guess but may not meet your initial goal

clc
clearvars 
Time=[0.5 1 5 8 10 20 22 39 40 42 50 51 55 60 69 70 73 100 102 110];
Buff=0;
Buffervalue= 0;
rate=[1 0.3 -16 2 -16 2 7 -16 -16 0.4 1 0.3 -16 2 -16 2 7 -16 -16 0.4];
% resample data with fixed delta x spacing = 0.5
t = min(Time):0.5:max(Time);
rate_it = interp1(Time,rate,t);

for slot= 1:numel(t)
    if Buff+(t(slot)*rate_it(slot))<=0 
         Buffervalue(slot)=0;
    else
    Buff= Buff+(t(slot)*rate_it(slot));
    Buffervalue(slot)=Buff;
    end
end
subplot(2,1,1),plot(Time,rate,'*b',t,rate_it,'r')
title(' Rate values');
legend('raw','interpolated');
subplot(2,1,2),plot(t,Buffervalue)
title(' Buffervalue ');