This can probably be combined into fewer actual lines. I kept them separate to demonstrate the approach —
A = complex(rand(10),rand(10))
A =
0.3470 + 0.8859i 0.0137 + 0.7639i 0.1015 + 0.7223i 0.5190 + 0.9946i 0.2642 + 0.9262i 0.1227 + 0.4625i 0.5610 + 0.0151i 0.9365 + 0.1072i 0.9752 + 0.7804i 0.8272 + 0.9432i
0.4636 + 0.2904i 0.1338 + 0.2256i 0.3974 + 0.6367i 0.9876 + 0.3169i 0.2435 + 0.0412i 0.3481 + 0.5287i 0.9613 + 0.8060i 0.3516 + 0.6644i 0.7104 + 0.0387i 0.1082 + 0.4680i
0.0129 + 0.6059i 0.0952 + 0.5557i 0.5719 + 0.9788i 0.2254 + 0.7534i 0.8180 + 0.1280i 0.5472 + 0.2541i 0.8326 + 0.8705i 0.0095 + 0.3066i 0.3927 + 0.4640i 0.7428 + 0.6265i
0.7454 + 0.4747i 0.4278 + 0.9148i 0.8096 + 0.6022i 0.7720 + 0.5985i 0.2754 + 0.3324i 0.9874 + 0.6228i 0.5922 + 0.1384i 0.9802 + 0.0692i 0.6346 + 0.6318i 0.1758 + 0.3041i
0.6405 + 0.2935i 0.5829 + 0.1763i 0.2208 + 0.8402i 0.5265 + 0.3813i 0.8351 + 0.2082i 0.9958 + 0.7694i 0.3690 + 0.7676i 0.6434 + 0.2222i 0.0020 + 0.1934i 0.6156 + 0.8573i
0.0943 + 0.9701i 0.3803 + 0.4209i 0.1179 + 0.9497i 0.9916 + 0.6548i 0.2876 + 0.1710i 0.0866 + 0.8797i 0.3089 + 0.4247i 0.3803 + 0.3770i 0.7961 + 0.3813i 0.2586 + 0.0791i
0.5874 + 0.2785i 0.2163 + 0.3044i 0.2791 + 0.4933i 0.2559 + 0.8200i 0.8186 + 0.4434i 0.2505 + 0.6017i 0.5400 + 0.9447i 0.1880 + 0.5847i 0.6254 + 0.6406i 0.3905 + 0.6088i
0.3084 + 0.0559i 0.5232 + 0.9541i 0.1421 + 0.3563i 0.6262 + 0.1674i 0.8474 + 0.7592i 0.1504 + 0.9597i 0.8628 + 0.9455i 0.9468 + 0.2465i 0.5404 + 0.7113i 0.6113 + 0.0233i
0.2909 + 0.3973i 0.9900 + 0.4806i 0.3832 + 0.9495i 0.3579 + 0.1691i 0.1201 + 0.1768i 0.3424 + 0.0581i 0.0161 + 0.4895i 0.9649 + 0.5228i 0.0355 + 0.1678i 0.8364 + 0.5422i
0.1649 + 0.9458i 0.4645 + 0.4179i 0.3430 + 0.6006i 0.5904 + 0.2400i 0.2482 + 0.3173i 0.3150 + 0.9556i 0.7045 + 0.5468i 0.8496 + 0.4076i 0.4556 + 0.8503i 0.0623 + 0.0865i
A2 = A.*conj(A)
A2 = 10×10
0.9052 0.5838 0.5320 1.2586 0.9276 0.2290 0.3150 0.8886 1.5600 1.5739
0.2992 0.0688 0.5634 1.0759 0.0610 0.4007 1.5737 0.5651 0.5061 0.2308
0.3672 0.3178 1.2851 0.6184 0.6855 0.3640 1.4510 0.0941 0.3695 0.9442
0.7809 1.0198 1.0182 0.9541 0.1864 1.3628 0.3699 0.9656 0.8019 0.1234
0.4964 0.3708 0.7546 0.4226 0.7408 1.5837 0.7253 0.4634 0.0374 1.1140
0.9499 0.3218 0.9158 1.4120 0.1120 0.7814 0.2758 0.2868 0.7791 0.0731
0.4225 0.1395 0.3212 0.7379 0.8667 0.4248 1.1840 0.3773 0.8014 0.5231
0.0983 1.1840 0.1471 0.4201 1.2945 0.9436 1.6383 0.9573 0.7979 0.3742
0.2425 1.2111 1.0484 0.1567 0.0457 0.1206 0.2399 1.2044 0.0294 0.9935
0.9217 0.3904 0.4783 0.4062 0.1622 1.0124 0.7954 0.8880 0.9305 0.0114
idx = A2 < 0.5
idx = 10×10 logical array
0 0 0 0 0 1 1 0 0 0
1 1 0 0 1 1 0 0 0 1
1 1 0 0 0 1 0 1 1 0
0 0 0 0 1 0 1 0 0 1
1 1 0 1 0 0 0 1 1 0
0 1 0 0 1 0 1 1 0 1
1 1 1 0 0 1 0 1 0 0
1 0 1 1 0 0 0 0 0 1
1 0 0 1 1 1 1 0 1 0
0 1 1 1 1 0 0 0 0 1
A(idx) = 0
A =
0.3470 + 0.8859i 0.0137 + 0.7639i 0.1015 + 0.7223i 0.5190 + 0.9946i 0.2642 + 0.9262i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.9365 + 0.1072i 0.9752 + 0.7804i 0.8272 + 0.9432i
0.0000 + 0.0000i 0.0000 + 0.0000i 0.3974 + 0.6367i 0.9876 + 0.3169i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.9613 + 0.8060i 0.3516 + 0.6644i 0.7104 + 0.0387i 0.0000 + 0.0000i
0.0000 + 0.0000i 0.0000 + 0.0000i 0.5719 + 0.9788i 0.2254 + 0.7534i 0.8180 + 0.1280i 0.0000 + 0.0000i 0.8326 + 0.8705i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.7428 + 0.6265i
0.7454 + 0.4747i 0.4278 + 0.9148i 0.8096 + 0.6022i 0.7720 + 0.5985i 0.0000 + 0.0000i 0.9874 + 0.6228i 0.0000 + 0.0000i 0.9802 + 0.0692i 0.6346 + 0.6318i 0.0000 + 0.0000i
0.0000 + 0.0000i 0.0000 + 0.0000i 0.2208 + 0.8402i 0.0000 + 0.0000i 0.8351 + 0.2082i 0.9958 + 0.7694i 0.3690 + 0.7676i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.6156 + 0.8573i
0.0943 + 0.9701i 0.0000 + 0.0000i 0.1179 + 0.9497i 0.9916 + 0.6548i 0.0000 + 0.0000i 0.0866 + 0.8797i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.7961 + 0.3813i 0.0000 + 0.0000i
0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.2559 + 0.8200i 0.8186 + 0.4434i 0.0000 + 0.0000i 0.5400 + 0.9447i 0.0000 + 0.0000i 0.6254 + 0.6406i 0.3905 + 0.6088i
0.0000 + 0.0000i 0.5232 + 0.9541i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.8474 + 0.7592i 0.1504 + 0.9597i 0.8628 + 0.9455i 0.9468 + 0.2465i 0.5404 + 0.7113i 0.0000 + 0.0000i
0.0000 + 0.0000i 0.9900 + 0.4806i 0.3832 + 0.9495i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.9649 + 0.5228i 0.0000 + 0.0000i 0.8364 + 0.5422i
0.1649 + 0.9458i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.3150 + 0.9556i 0.7045 + 0.5468i 0.8496 + 0.4076i 0.4556 + 0.8503i 0.0000 + 0.0000i
Experiment to get different results.
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