How to return corresponding entries of an array using if statement

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University
University 2024-2-12
评论： University 2024-2-14
Please how can I handle this:
I want to use if statement such that
if intabsul == absintul && intabsur==absintur
returns the corresponding entries of the xivals and Lvals
elseif intabsul ~= absintul && intabsur~= absintur
return the corresponding entries of the xivals and Lvals
elseif intabsul == absintul && intabsur~=absintur
return the corresponding entries of the xivals and Lvals
elseif intabsul ~= absintul && intabsur==absintur
return the corresponding entries of the xivals and Lvals
else do nothing.
See my code below, although is not complete:
xivals = linspace(0, 10, 10);
Lvals = linspace(2e-8, 666.7e-6, 5);
for il=1:length(Lvals);
for ixi=1:length(xivals)
%
intul(ixi, il) = trapz(yvals, uxl(:, ixi, il));
intabsul(ixi, il) = trapz(yvals, abs(uxl(:, ixi, il)));
%
intur(ixi, il) = trapz(yvals, uxr(:, ixi, il));
intabsur(ixi,il) = trapz(yvals, abs(uxr(:, ixi, il)));
%
absintul(ixi, il) = abs(trapz(yvals, uxl(:, ixi, il)));
%
absintur(ixi,il) = abs(trapz(yvals, uxr(:, ixi, il)));
end
end

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回答（1 个）

Walter Roberson
Walter Roberson 2024-2-12
mask = intabsul == absintul & intabsur==absintur;
subset_xi_1 = xivals(mask);
subset_Lv_1 = Lvals(mask);
mask = intabsul ~= absintul & intabsur~= absintur;
subset_xi_2 = xivals(mask);
subset_Lv_2 = Lvals(mask);
and so on.
  2 个评论
University
University 2024-2-12
编辑：University 2024-2-12
Thank you so much for your help. I tried it but I received:
Error in active_flow_run (line 242)
subset_xi_1 = xivals(mask);
"The logical indices contain a true value outside of the array bounds".
Another thing is that fact : intabsul == absintul & intabsur==absintur might not be necessarily true for every entries of the matrices.
I thought of something like: intabsul-absintul < epsilon
where epsilon= 10^-11. If want to use this approach, i.e.,
if intabsul-absintul<epsilon & intabsur-absintur<epsilon
return the corresponding values of xivals and lvals
and so...
How do I handle this case?
University
University 2024-2-14
Hi Walter,
Please how can handle this error?
Error in active_flow_run (line 242)
subset_xi_1 = xivals(mask);
"The logical indices contain a true value outside of the array bounds".
I have tried several ways but I still receive this error.

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