How to return corresponding entries of an array using if statement

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

Answer 1

[Walter Roberson]

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.

[University]

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]

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.