Calculation of summation with filtering positive and negative values

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JAVAD
JAVAD 2023-4-24
评论： the cyclist 2023-4-25
Hi
I have one matrix with u(i,j,t).
I need calculate sum of the variable like this in each time step.i,j have not folloed an approprate pattern for example the same i or j
sum(t)= u(167,148,t)+u(167,139,t)+u(167,165,t)+u(167,164,t)+u(167,163,t)+..
But,I need an algorithm to seperate positive and negative values.
for example in each time step check the u: if u is positive: sumpositive(t)=u(167,158,t)+u(167,159,t)+u(167,160,t)+u(167,161,t)+u(167,162,t)
if u is negative : sumnegative(t)=iu(167,158,t)+u(167,159,t)+u(167,160,t)+u(167,161,t)+u(167,162,t)
Thanks

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the cyclist
the cyclist 2023-4-24
Ran in:
% Set seed for reproducibility
rng default
% Some pretend data
u = randn(4,4,3);
% Identify positive u
uIsPos = u >= 0;
% Sum the positive u
sumpositive = sum(u.*uIsPos,3)
sumpositive = 4×4
0.5377 1.3155 4.0673 1.0193 3.3236 0 3.8041 0 1.4090 2.0875 1.0461 1.6031 3.7177 1.9729 3.3478 0.6277
% Sum the negative u
sumnegative = sum(u.*~uIsPos,3)
sumnegative = 4×4
-1.1930 0 -0.1022 -0.8649 -0.8095 -3.2701 -0.2414 -0.8804 -5.2031 -0.4336 -1.3499 -0.1649 0 -1.7115 -0.3034 -1.3520
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JAVAD
JAVAD 2023-4-25
移动：the cyclist 2023-4-25
I try to sum in each time step.
Here u(i,j,t); t is time
what I need is that;
for t= 1:length(time)
sum(t)=u(167,158,t)+u(167,159,t)+u(167,160,t)
end
it works but it cannot seperate positive and negative values.it sums u which can be positive and negative
I need one algorithm
if u>0 ; sum all u+
if u<0; sum all u-
the cyclist
the cyclist 2023-4-25
for t = 1:length(time)
sumpositive(t) = (u(167,158,t).*(u(167,158,t)>0)) + (u(167,159,t).*(u(167,159,t)>0)) + (u(167,160,t).*(u(167,160,t)>0));
sumnegative(t) = (u(167,158,t).*(u(167,158,t)<0)) + (u(167,159,t).*(u(167,159,t)<0)) + (u(167,160,t).*(u(167,160,t)<0));
end
which can be simplified to
for t = 1:length(time)
sumpositive(t) = sum(u(167,158:160,t).*(u(167,158:160,t)>0));
sumnegative(t) = sum(u(167,158:160,t).*(u(167,158:160,t)<0));
end

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