Missing counts during histcount?

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Joy Shen
Joy Shen 2023-8-30
评论： Voss 2023-8-31
Hi, I am randomly generating Nsim=10000 values and then binning them with histcounts but there seems to be missing values and I'm not sure where they went. I believe when I sum my histcounts
sum(Hist_CVol1)
I should be getting Nsim since it's binning each simulated value into VBinEdges, but right now I'm getting 3742 when I sum my histcounts. Not sure where they disappeared to or I'm misunderstanding what histcount does.
VBinEdges=[0 1E-17 0.3:0.05:0.8 1.1].*Vroom(:,1); %ft^3 goes to 1.1*Vroom because "infinity" to capture everything. Then we cap it later
VBinEdges_Lo=VBinEdges(1:end-1);
VBinEdges_Hi=VBinEdges(2:end);
VBinEdges_Md=VBinEdges_Lo+(diff(VBinEdges)/2);
IndEFH2 = [1:length(ExtSurgeBinEdges_Md)]'; % EFH index
IndV1 = [1:length(VBinEdges_Md)]'; %Flow volume 1 index
IndA_ps= [1:length(DamState)]'; % PS flow area index
temp1=[]; temp2=[]; temp3=[]; [temp1,temp2, temp3]=ndgrid(IndA_ps, IndV1, IndEFH2);
IndMatCVol1=[temp1(:),temp2(:), temp3(:)];
% CVol1 Node Sim
for iCombCVol1=1:size(IndMatCVol1) % iCombCVol1=1:624
% EFH loc 2 sim
EFH2_a=[]; EFH2_a=ExtSurgeBinEdges_Lo(IndMatCVol1(iCombCVol1,3));
EFH2_c=[]; EFH2_c=ExtSurgeBinEdges_Hi(IndMatCVol1(iCombCVol1,3));
pdEFH2=[]; pdEFH2=makedist('Uniform',EFH2_a,EFH2_c);
Esim2=[]; Esim2=random(pdEFH2,[Nsim,1]); %simulate external flood heights within bin (Uniform within bin)
Esim2=Esim2.*(Esim2>=0); % make sure it's positive
% Flow volume 1 sim
V1_a=[]; V1_a=VBinEdges_Lo(IndMatCVol1(iCombCVol1,2));
V1_c=[]; V1_c=VBinEdges_Hi(IndMatCVol1(iCombCVol1,2));
pdV1=[]; pdV1=makedist('Uniform',V1_a,V1_c);
V1sim=[]; V1sim=random(pdV1,[Nsim,1]);
V1sim=V1sim.*(V1sim>=0); % make sure the difference is never below zero
V1sim=V1sim.*(V1sim<=Vroom(:,1)); % make sure the difference is always below Vroom
%Flow volume 2 sim
% PS state sim through area
Mu_ps=[]; Mu_ps=Amean_ps(IndMatCVol1(iCombCVol1,1));
Sig_ps=[]; Sig_ps=0.2*Mu_ps;
pd_Asim_ps=[]; pd_Asim_ps = makedist('normal',Mu_ps,Sig_ps);
Asim_ps = []; Asim_ps=random(pd_Asim_ps,[Nsim,1]);
Asim_ps(Asim_ps<0)=0; % make sure the area is postive
Asim_ps(Asim_ps>A_ps)=A_ps; %make sure area is never bigger than the full area
% Volumetric flow rate 2 sim calculation
Qsim_ps2=[]; Qsim_ps2=Cd.*Asim_ps.*sqrt(2*g*(Esim2-n_ps)); %ft^3/s
Qsim_ps2(Esim2<=n_ps)=1E-20; %No flow when Esim is less than or equal to installation height
% Flow volume sim calculation
Vsim_ps2=[]; Vsim_ps2=Qsim_ps2.*Dsim; %ft^3
Vsim_ps2=Vsim_ps2.*(Vsim_ps2<=Vroom(:,1)); %Ensure Vsim is less than Vroom (3 Vroom configs)
Vsim_ps2(Esim2<=n_ps)=1E-20; %No flow when Esim is less than or equal to installation height
% Cumulative flow 1 sim calculation
CVol1sim= V1sim+Vsim_ps2;
% PMF
Hist_CVol1=[]; [Hist_CVol1,~] = histcounts(CVol1sim,VBinEdges);
Hist_CVol1=Hist_CVol1';
PMF_CVol1(:,iCombCVol1)=Hist_CVol1./sum(Hist_CVol1); % Bins it by the parents
end
  2 个评论
Image Analyst
Image Analyst 2023-8-30
I tried to reproduce and I just got "Unrecognized function or variable 'Vroom'." What is that function?
Joy Shen
Joy Shen 2023-8-31
@Image Analyst
Vroom = [6250 8125 5000];
This is why I use Vroom(:,1) because I'm checking each value of Vroom. Eventually I'll index and store values for each value but for now I'm sticking with just the first value to make it simple.

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回答（1 个）

Voss
Voss 2023-8-30
Ran in:
I suspect that the data you are using histcounts on has elements outside the range of bin edges you have specified.
For example:
% generate 10000 samples from a standard normal distribution
d = makedist('normal',0,1);
x = random(d,[10000,1]);
size(x)
ans = 1×2
10000 1
% specify some edges that don't include +/- infinity.
% the domain of normal distributions is (-Inf,Inf)
e = [0 1E-17 0.3:0.05:0.8 1.1];
% do the histogram binning
N = histcounts(x,e);
% count the number of samples within the specified bins:
N_inside = sum(N)
N_inside = 3584
% count the number of samples outside the specified bins,
% either below the first edge or above the last edge:
N_outside = nnz(x < e(1) | x > e(end))
N_outside = 6416
% the total number of samples:
N_inside + N_outside
ans = 10000
  3 个评论
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Voss
Voss 2023-8-31
Those lines work to limit the values of each vector, but you do histcounts on the sum of two of those vectors:
CVol1sim = V1sim+Vsim_ps2;
[Hist_CVol1,~] = histcounts(CVol1sim,VBinEdges);
It looks to me like there's no guarantee that all elements of CVol1sim are within the range of VBinEdges. In fact, it looks like CVol1sim could be as high as 2*Vroom(:,1).
Voss
Voss 2023-8-31
Ran in:
By the way, this logic:
V1sim=V1sim.*(V1sim<=Vroom(:,1));
sets the elements of V1sim that are greater than Vroom(:,1) to zero (or NaN if the element was Inf). Is that what you want to do?
Here's an example:
Vroom = 6250;
V1sim = [-Inf -1000 0 1 7000 Inf]
V1sim = 1×6
-Inf -1000 0 1 7000 Inf
V1sim=V1sim.*(V1sim<=Vroom(:,1))
V1sim = 1×6
-Inf -1000 0 1 0 NaN
I imagine you want to set those elements that are greater than Vroom(:,1) to Vroom(:,1), in which case, you can use logic like you have in other places:
V1sim = [-Inf -1000 0 1 7000 Inf]
V1sim = 1×6
-Inf -1000 0 1 7000 Inf
V1sim(V1sim > Vroom(:,1)) = Vroom(:,1)
V1sim = 1×6
-Inf -1000 0 1 6250 6250
(This doesn't address the original question or impact my suggestion that elements sent to histcounts are outside the range of the bin edges.)

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