Hi,

I wish to construct a matrix whose blocks depend on (a lot of) conditions. Since I don’t know the final size of my A matrix at the beginning or the first block to start with, I intend to delare it empty and then add (append, push, concatenate, …) new rows from another B matrix. I checked other posts but couldn’t find a satisfying easy way to proceed. Do you have suggestions about the way to declare A or to concatenate starting an empty matrix ? Or do you see a complete different ways to achieve the same result ?

Thank you in advance

```
# OBJECTIVE
A=... # "A" defined somehow
B=some_matrix
C=some_other_matrix
if condition1 A=vcat(A,B) end
if condition2 A=vcat(A,C) end
# A should be the size of B, C or [B,C]
# TRIAL 1
A=[]
B=rand(5,2)
# next lines are indepedent from one another
append!(A;B) # not working
A=vcat(A,B) # not working
A=[A,B] # not a matrix
# TRIAL 2
A=Array{Float64,2}
B=rand(5,2)
# next lines are indepedent from one another
append!(A;B) # not working
A=vcat(A,B) # first row not expected
A=[A,B] # not a matrix
```