Three-dimensional lower triangular Matrix

Hi guys,I want creat a 3D lower triangular Matrix such as the size of 100*100*100. I know to use the tril function to creat a 2D lower triangular Matrix . Is there any function that can help me solve this problem？ Thanks.

Answer 1

[DGM]

Not sure if this is what you're asking, but:

A = randi(89,10,10,2)+10; % test array
mask = tril(ones(size(A,1),size(A,2))); % make a mask 
B = bsxfun(@times,A,mask) % bsxfun() isn't strictly necessary post-R2016b

gives:

B(:,:,1) =
    34     0     0     0     0     0     0     0     0     0
    78    93     0     0     0     0     0     0     0     0
    90    17    64     0     0     0     0     0     0     0
    75    37    21    28     0     0     0     0     0     0
    47    63    56    20    20     0     0     0     0     0
    94    29    85    37    63    85     0     0     0     0
    33    67    92    46    36    82    99     0     0     0
    58    82    55    48    24    92    54    76     0     0
    95    55    35    38    11    23    72    57    59     0
    34    68    69    72    36    55    47    82    64    26
B(:,:,2) =
    22     0     0     0     0     0     0     0     0     0
    89    40     0     0     0     0     0     0     0     0
    14    38    13     0     0     0     0     0     0     0
    72    90    78    54     0     0     0     0     0     0
    76    32    73    33    44     0     0     0     0     0
    49    38    30    93    30    28     0     0     0     0
    44    47    71    52    30    65    75     0     0     0
    98    74    60    33    57    59    58    55     0     0
    46    23    86    49    49    25    33    48    86     0
    50    88    60    73    76    11    92    65    90    59

[Florence]

Thanks very much!